Phone battery longevity

It seems that almost everyone just takes it as granted that you have to charge your phone daily. And here I am, happily using my phone for 4-5 (yes, four to five) days between recharges, and I charge phone typically when it is down to 20% charge or so.

My usage doesn't really strain battery that much either; occasional web browsing, some navigation/tracking, audiobooks, but mostly plain old phone calls (it's my work phone, after all). I don't like playing games with a phone which may be large part of power usage for some people. For long time I though this to be the reason for extended usage time.

I have one Android phone too (cheap-ish Galaxy Trend-series), used mainly for app development/testing, and it, too, seems to happily go for about same time without needing recharging. Initially I thought this to be because I don't really use it for anything - it just sits on my desk, powered up but doing nothing. This would seem to match with my guess above.

Not so.

Last year I had to send my Jolla to be repaired - speaker developed horrible metallic sound which rendered phone useless as a phone. So I took the Android phone and used it for about two weeks. Usage pattern was pretty much the same as with my Jolla. And the battery life plummeted - even with that low usage I had to charge damn Android phone daily! (and afterwards, when it just sits there, it's back to four-day charge cycles)

If battery life were the primary consideration, I now certainly know which OS I prefer (I don't have hands-on experience on the remaining two OSs but based on what I've heard they aren't any better than Android.)  Now, if Jolla were just to offer slightly smaller phone, as current model is a bit too large for my liking... (and really, damn paid app store - I think that their disregard of proper app store was their Single Biggest Mistake)