ooo, i like those tilt-drip-tip insulators, andriaD, very nice!
OP- I've been on ECF from the beginning onward, this being my 2nd user-name, this being my close-to 4,000th post. lol. There's many answers to your question. The 1st answer being... There is ANCIENT WISDOM that old-timer vapers gather, over time, and they try to share that knowledge with those new vapers whom will listen. Of the most cardinal, most important, most sacred, of rules, to vaping- The golden rule of vaping: Have backups, for your backups, for your backups. That is, be SURE to have backup mods... WHY? Because if your favorite mod of all time were to somehow be placed down, on a shelf, at the big-box store, (Target, Walmart, etc) and you make it half-way home before realizing you DONT have it... You're most-likely S**T-OUT-OF-LUCK, right!? Well, you want to AVOID these types of frightening situations, sir... See, cigarettes were easily bought at the local gas-station. Mods, well, they aren't so easily purchased. Not at all times, not at all hours of the night, not on holidays, not when you're out-of-town, and not when you're at the family reunion... So, because of this issue, we suggest you have at-least a favorite PV (called the MAIN PV) and a secondary PV (the BACKUP PV) Because eventually, you WILL LOSE a mod, and/or a mod of yours MAY be STOLEN from you. It happens.
SECONDLY- Mods wear-down over time, TRUST me. TRUST US! Trust me when I tell you, that the shiny new mod you hold in your hand today, WILL NOT look as nice as it's looking right now, in 1 year, and especially not in 2 years... (this was a-lot more meaningful back 1-2 years ago, when we were buying cheap, chromed mods, that lost their chrome finish, or their paint, or their lamination.. but, still relevant) Trust me when I tell you that if you use a machine daily, for 4, 5, 6 months, that machine IS going to WEAR DOWN. The buttons weaken and become rattly, the paint chips and fades, everything I've mentioned, does-happen, and WILL-happen, over time. This is why we continuously buy new mods, because, the mods we have today, will not be there for us in the long-term, esp not aesthetically, lol... They aren't made to look pretty forever, and they certainly aren't going to. In-fact, some of our members are EXPERTS with "mother's mag" stainless steel polish, wet-sanding stainless steel and aluminum, and paint refinishing, bcuz of this!
Functionality-wise, our mods break down in this way as-well... This was more-so prevalent back when we were buying CHEAPLY-MADE mods from terrible companies out to ROB US of our money by selling us CRAP. But, it still reigns true today. Mods are mechanical, mods are electronic, and mods WILL break. you do NOT want to be without your main PV, without a backup PV, right? Mods WILL let u down. In every way you can possibly think of, and more. You WILL drop your main PV off of your bed, 200 times. You WILL get out of your vehicle with your mod in your lap, and drop it to the pavement below, 200 times. You WILL scratch, chip, gauge, mane, and utterly DESTROY your mod(s) over time. Trust me. It happens, over time... & when the final blow hits, & leaves you without a means of delivering nicotine to your body, you will wish you had a backup mod, and a backup mod for that backup mod. Think Murphey's Law... Anything that CAN go wrong with your mod, WILL go wrong with your mod, eventually...
There is also a WANT factor, sure... If you hang around ECF Forums for a long-enough period of time, you WILL (most-likely) wind-up wanting a mod (or two, or three) that someone else has. You WILL wind-up feeling the throws of "mod envy" and "shinyitus" as my compadre has so carefully put it... This is a fact of life. If you are human, you WILL covet your neighbor's mod. There is also the OCD illness of Obtainitus... THIS illness will have you creating categories that "MUST BE FILLED!" haha... For example: Do you currently have a regulated mod? YES? Well, good!! But do you have a regulated TUBE mod!? NO? Dude, you HAVE to try a regulated tube mod.. They are SO stealthy! I promise, you'll LOVE it! Do you have a mech mod? NO!? DUDE!? u neeeed a mechanical mod. You NEED a mechanical BOX mod! DUDE do you even SQUONK? DUDEEEE, if you DON'T have a bottom fed mod, you're legit NUTS! Bottom-feeding mods are where it's AT right now my dude... & BRO, they have REGULATED bottom-feed mods, you NEED to try a mechanical BF mod, and a REGULATED bottom-fed mod!!! And dude, do you have a stainless-steel and brass mechanical tube mod? Dude, you have not LIVED until you've held a stainless steel, and brass, mechanical tube mod, in your hands, they're simply GORGEOUS paired with a stainless steel/brass RDA or SS/Brass Tank, seriously. they really r beautiful... OH and dude, you HAVE to get a 26650 mod for when you're just chillaxin' at home, and you don't want to have to recharge the coffee table mod's battery in 2-3 DAYS.. SO awesome! I mean, I wouldn't take my 26650 mod OUT w/me, but, it's the PERFECT coffee table mod, & i NEVER charge it!! OH and BRO- You SIMPLY MUST grab a box mod with internal tank... Like, the Kanger Nebox, or, the Billetbox, or, the Xvostick... They're SO tiny! They're SO short that only the drip-tip pops out of your fist when you're vaping in public, it's sweet for stealth vaping! SPEAKING-OF: Do you have a STEALTH MOD? DUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUDE.... you NEED a STEALTH MOD!! like, you HAVE to grab a nice 18350 mechanical tube mod, for when you want to be suuuuper stealthy out in public, or at disney land!! OH, and that reminds me! do you have a GENESIS HYBRID MECHANICAL YET!? DUDE... u NEED to genesis hybrid mechanical with a vertical stainless-steel wick, it's a WHOLE NEW BALLGAME when it comes to conductivity and vapor production/taste!!! OH and an E-PIPE! OH and you NEED a dinner-party-mod for fancy dinners and balls... OH and grab yourself a cheap beater mod for work/rock-climbing/etc...
You see, the above BLOB of words, is what happens when you begin filling categories. THAT is when you've become a collector, and, once you're a self-admitted collector, you have the bug... & you no-longer need backups for your backups, NOW you need 1 mod in each and every category I've listed above, and at-least 1 backup, in each & every category I've just listed above!

lol. OH and warning: Once you're a collector, you're gonna begin buying "high quality mods" such as Provari's, Reos, iHybrids, HOHybrids, etc/etc. Good luck with that. As you'll see in the "show us a picture of your current setup" thread, there's plenty of collectors here...
& then there is the VAPOCALYPES hoarders... Those of us vapers whom know that the FDA is planning to BAN the sale of ALL advanced E-Cigarette Mods & Accessories, in the not-so-distant future. Plenty of us here on ECF believe mods will become harder to obtain, and they'll become more expensive to obtain... Which is why vapocalypes hoarders are buying many mechanical mods, and rebuildable atomizers, in hopes of being able to vape WELL into the future, WITHOUT having to buy new mods/attys, in the future.
So, there are plenty of different reasons for needing more than 1 mod, and WANTING more than 1 mod... My advice to you, is to stick as close to where you're currently at now- but, i DO recommend you buy a couple 2-3 mechanical mods, a couple regulated mods (have 1, 2, maybe even three regulated mods) and, enjoy yourself after that. you DONT want to be stuck w/ no ability to vape the way you want to vape, for 2, 3, 4 days... F that. Enjoy the vape journey... duuuuude.....