i've got a tablet and beat the crap out of it on an almost nightly basis, last night i plugged around in flash (which i have no idea how to use!) and figured out how to make frames and stuff, yes a tablet is going to makes things MUCH easier for you unless you plan on making lazy sprite or stick figure shit.
as for how long they last, I have an ancient Wacom GD-0608-R and I'm fairly sure if I threw it accross the room it would still work, don't know much about the silly bamboo ones though.