The Bottom Bracket on my three month old Pista has developed an occasional squeak in a portion of the spin.
I ride in a lot of wet and crud, and given the bargain basement price of a Pista, it would not surprise me if the BB started to fail early; although, some people on this forum have reported several years service out of their Pista's BB.

Assuming a failing BB, when the time comes to fix it, do I just change the cartidge bearings or do I get a whole new, higher quality BB?
I have an excellent chain line right now, and I don't want to do anything that would cost me that good chain line.

If I replaced my present BB with an upgrade, which BB, dimensionally, would give me the same interface with my crank and thus preserve my chainline?

---and---

If I can accomplish the same thing by replacing the bearing cartridges with something better, why not do that instead?

Have I sufficiently revealed my ignorance?
Thanks.