> it seems unreasonable to store enormous amounts of renewable energy in a device that itself has to be replaced after a certain number of cycles. The device used for pumped energy storage -- a tank (to simplify greatly) -- basically never needs to be replaced.

It's a fair point but I think that you oversimplify the pumped hydro case. Pumped hydro also has quite some electronic components (turbines/motors), electronics, and other moving parts (valves, overflows). I can imagine some of these components require semi-regular maintenance (hence the maintenance shaft in the diagram on the website of OP).

You'd really have to run the numbers to see which costs more to maintain in the long term.