For me I just... use them. And I have a tendency to not forget such things. The unused ones will lose their charge over time, indeed.
My phone I use. My old phone, that I use as GPS, I have to remember to charge before I need it.
My laptop I use all day, my previous laptop has no battery anymore.
My iPad Mini has got the short stick some times, to be honest, because it is mainly a secondary device. I have it always with me, but I rarely use it outside the house. And in the house it's not the top device, either.
The Steam Deck I use throughout the week, so I see its charge. But now I used it again the day before yesterday after half a year, or something. It happens, no need to have it charged in the meantime, frankly. Same for my controller. The little Anbernic handheld faces a similar fate.
Wireless keyboards I do not possess currently, and the one wireless mouse I have takes an AA battery, and is Logitech, 2-year battery, no worries.