I'm not a huge fan of the Ego One clearo, myself (for different reasons not related to build quality) but I wouldn't expect the o rings to last indefinitely, especially if they've been regularly removed and cleaned. It might have ripped sooner than expected, but it wouldn't be a huge deal to me. Personally, I love the Ego One battery and wouldn't write a product line off for a faulty component of one product in the line. I agree that they should include spare o rings, but the fact of the matter is that they don't. When making a
tank purchase, I certainly note whether spare rings are included, but don't use that as a deciding factor. If the
tank does what I want and doesn't come with spare rings, I order a spare pack at the same time or determine the size and order some elsewhere. Good practice.
A call or email to Joyetech US might have been a prudent course of action. They'd probably have sent the o rings for free.
Incidentally, at $60 for the starter kit, you got ripped off a bit by your merchant. Just sayin'...