Wet grit is what gets my pads the fastest. Hills not so bad alone if it's dry and the road is clean.
I'm finding v-brake inserts harder to buy on the road these days. Few bikes have rim brakes anymore and many shops only carry low end non-insert type pads intended for the cheapest bikes.
On my 2024 tour I had to buy some of these cheap pads and ended up carrying the holders in my tool bag. Two of the cheap pads are still on my bike now.
Anything to do with rim brakes, non-through axle wheels, 26 inch wheels, 36 spoke rims, etc., is getting harder to find these days.
A neighbor works as a mechanic in a large bike shop on a large university campus. He says they have a good stock of 27 inch tires and anything else needed for older bikes because so many bikes on campus are that old. If you live in a community with a college campus, a bike shop there might be the best place to buy older parts. I told him that I can't find the shift cables to fit my Huret downtube shift lever on my rando bike, the next day he gave me a couple cables from that era.