Re: I hate to say it...
Three years?
My iPhone 6s from late 2015 still has 83% battery capacity. (Mind, I really wish it had higher capacity and were easily replaceable.) Eligible for IOS 14 though that will be the end of the line, I fear.
Why, only a very few months ago, I sold a Samsung Galaxy S2 from 2011 with its original battery (plus a replacement with slightly higher nominal capacity). Despite having been left in a drawer for the best part of five years it charged and worked OK albeit with less life. And a Nexus 7 from, IIRC, 2013 which still had decent battery life - also left in the same drawer but for a slightly shorter time, three or four years.
My biggest gripe about the S2 was lack of updates.
I do have Samsung tablets which have been getting updates but keep expecting them to stop. I only got them for specific purposes for which they made more sense, especially given the relatively high prices of iPads. The SM-T850 is over four years old. (Just checked - last update 2 May 2020 - perhaps I have now hit the buffers?)
What do you do with your batteries?
Biting the hand that feeds IT
