When I had rim brakes, I always made sure the rim was clean after a ride and an occasional resurfacing of the block with a bit of Emery paper when changing a wheel is also good idea.
Blocks get bits of hard grit etc embedded in them and freshening them up does them good, leaves a less polished surface and prevents damage to the rim.
However, I'm sure I have posted on here about my wholesale conversion to disk brakes and wouldn't be without them on road or MTB. Rims are fine in the dry but in the wet on a steep descent....!?