Product review (4 stars): Bearing Kit for Dryer
I ordered this kit as I was doing a general overhaul of the dryer: belt, glides, and the bearing.  In truth, the old bearing was highly serviceable, and I could likely have gone on for much longer with the old bearing, just putting some new grease into the nylon bearing cup.  In fact, to me it wasn't clear thet the nylon bearing cup was included in the kit and I ordered one of those separately:

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Anyway, not a lot of money spent.

In rehabing the dryer, I would suggest that the bearing might be in pretty good shape, and that, at most, only replacing the nylon bearing cup/retainer would be called for, plus adding new grease.

What really probably slows down the drum and puts strain on the motor are the glides.  Glide kits are available here, and should probably be changed every few years to keep the drum spinning freely.