Well, it sounds like you really like your equipment... That's half the battle right there. I think getting those backups was smart. You may find you want to branch out, modwise and tankwise, but it's not *necessary*. As far as your vape getting warm, a sub-ohm device with higher watts is going to do that. As long as you're not getting spitback or drops of overheated vape on your tongue, you ought to be okay. And, when you get ready to make your own coils (if you want to) someone was mentioning on another thread that a smoke tank came with an RBA for building your own coils, though personally I am going to start with something simpler, I think.
I bought a backup mod I thought I would like... for in my purse... Now it sits next to me and I get to alternate flavors... It is rarely in my purse.... I don't mind

So yes, if you are chainvaping (I know I did that a lot starting out, or in the a.m.) it is good to have another mod set up and ready to go, that should reduce overheating of just one tank. I'd think that using 2 regularly but not pushing them to the limit should make the gear more durable, but it's just a thought, I certainly don't know that for sure.... But I like a cool vape, anyway.
Hope things continue to go well, congrats on ending a 45 year smoking career! Never thought I'd say this myself, but vaping is SO MUCH better!
Anna