it's pretty personal. some people just get the cheapest bearings they can find, and just replaces them once, twice, maybe more, a year. but i tend to agree with the user above me. if you buy bones swiss (i think they're about 40$) they're not only very fast, but they should last you at least a year. and if you take a step up from the bones swiss, then they are lubricated, and lubricated bearings (although initially faster) tend to pick up junk off the road and will slow down over time more than bones swiss will.
bones swiss original or reds
get some bones reds their great bearings and only 15 bucks too
