It's not the lithium part of lithium batteries you worry about, it's everything else. Lithium hexafluorophosphate turning into hydrogen fluoride gas, for example.
I still have my lead acid batter in my UPS from... 2016? I'm not even sure when I got it.
With lithium I need to know when I got it, did it run in non-ideal lithium conditions (-20^C? No go. +34^C? No go), and the most importantly - in three years I need to replace a Li battery, but with a lead battery and a non-online UPS I can have from 3 to 10 years of lifetime from it.