Well, I am pretty new to vaping, only been at it around 2 months, but man-oh-man I sure have bought alot of stuff, must be some obsessive/compulsive thing goin on there with me--I am of the mind that it's better to stock up, so I have a nice little stash of different cartos, just because I don't want to run short.
I think that CCV's bundle deals on the cartos is a great price, so when I order from them, I always get a bundle--that way if I lose one, or happend to burn one or have a dead one, then I'm not without some backups. I ordered the Jumbos's in a bundle without even knowing if I'd like them, also I suspected that I would really like them, and I do, lol. And they do last a very long time, like you said, so 15 of them should last me a good long time.
I don't worry too much about CCV running out of stock, even if they do, it's not a long wait before they re-stock, but it's good to have some on backup, so if you can afford to get extra with your next order, that's what I would do. I got in on a carto-CO-OP in May, and ordered 10 boxes of cartos, just because the price was so low with so many people buying them. All of those cartos will go directly into my "stock pile" as I'm about to be out of work for the summer, and wanted to make sure my vaping supplies would last til I get back to work in September.
man I just can't get past the rubber taste of those Jumbo drip tips! LOL so I will keep on clipping the little carto condoms to fit on the bottom of my 510 drip tips so that I can use those.