I must admit that in all my years of cycling, this issue of grit on brake blocks causing wear on rims has never really entered my consciousness.

A few years ago, when I collected my bike from the local bike shop after a repair, they pointed out that the rim on one wheel was getting dangerously thin. But the rim had done many years of service, so I put it down to normal wear and tear (and I did get it replaced).

As for steep descents in the wet: I have just got used to starting to apply the brakes well before I actually need to slow down!