Every couple years is probably more accurate. Hardware fails all the time, especially at scale. Hard drives fail all the time, solar equipment isn't magically different. Once a full neighborhood has solar, someone will have a defective panel, a defective inverter, an improper install that needs to be redone, storm damage, panels that need cleaning, panels that get damaged from cleaning, or a building gets renovated/replaced/destroyed.

A 5 kW inverter at a house is different from a 500 kW inverter in the desert

And the batteries?

this is far from the truth. NREL have great reports and ongoing research into how often solar panels fail. You are correct in that it isn't every couple of years but it is not as long as 20 years. The number of solar PV panels that have been around that long, let alone survived that long is small.