Originally Posted by Seattle Forrest

Rain means that dirt and grit splash around, get onto your rims (and into your drive train), and act like sand paper. If you're not going to ride in the rain, it will greatly extend the life of your rims, chain, cassette, and chain rings. Maybe the bearings, too, depending how well they're sealed. Right off the bat, I wouldn't worry much about it; choose the bike/components for other reasons than longevity.

Are you going for a road bike, hybrid, or what?