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So would I be an idiot to replace my chain (13k miles) without replacing my sprockets?
They (sprockets) are not terribly worn. (No hooking or sharp edges, etc..) Replacing the chain myself involves buying/borrowing a $90 chain tool and removing/installing the chain.
Changing the sprockets is much more involved and essentially involves complete disassembly of the rear wheel/hub/brake assembly and would require several other tools. (46mm socket, etc..)
There is no set schedule for sprocket or bearing replacement, just notes to replace when you have everything apart if the bearings appear to be worn/failed. Without taking it apart I don't think there is anything wrong with my bearings.