It's unusually for the motor to outlast the wet end -- can happen, but not that common in my experience.

If I was working on your pool as a service guy, I'd be unwilling to replace wet-end only, because I'd figure it would all be likely to fail before summer was over, and you'd be PO'd at me, because I didn't 'fix your pump right'! Of course, if I saw your pump, I might be able to tell why the wet end was failing, and be able to determine that the pump hadn't experienced much wear and tear. Otherwise, I'd walk away from the job rather than replace wet-end only, because I'd figure it was a warranty problem waiting to happen.