That's a good point. I think it seems likely that given the relatively larger storage capacity per unit[0] with pumped hydro vs. batteries, that the overall maintenance costs -- including the environmental costs of materials needed -- would be lower, but you're absolutely right that we'd have to do the math to know for sure.

[0]When I say "per unit," I just mean that a huge battery is made up of many cells that will need to be replaced individually, whereas large pumped hydro facilities are still only a small number of total reservoirs.