I am responsible for maintaining eight 150 Ah 120v dc battery banks. The sites also have diesel generators so the batteries really only get used for the 10 seconds it take the diesel to start, maybe 4 or 5 times a year. The batteries are indoors. So far cells start to go after 5-7 years and then I have to replace the whole bank.

Even 1 decade is optimistic life from current technology batteries that I am being sold from industrial battery sales channels.