Or, it could be the pedals clicking, too. Remove the pedals and clean then grease the threads, then screw them back in and make it tight. At least you'll rule out a possibility this way.
If the problem turns out to be the bottom bracket bearings itself, not the pedals or the crank mounting on the BB, then you should just ride it into the ground. Typical Cartridge BB's aren't replacable, so use it for as long as you can before it starts to slow you down. In my understanding, the bearings usually go bad, the spindle rarely, rarely, snaps.
On my end, I've got a Shimano UN-52 (LX, square-taper BB) and it's got 8,000 miles and is still almost perfectly smooth. But it's on a road bike that rarely gets ridden in the rain or anything...