I don't know about other phones but my 2020 Motorola Moto G Power has a 5Ah battery and I charge it 2-3 times a week, at most. I charge it here at my desk at work but that's only when I remember to. If I don't remember to, it doesn't matter because, to date, I've never seen it go below 25% and it takes maybe an hour to get it back to full from 25%. I've had the phone since early 2021 and it's still doing just fine.
That battery was something that I couldn't say no to because it just never runs out of juice. When it comes to phones, I actively avoid brands like Samsung because I'm not interested in paying $200 just because it says "Samsung" on it. I'd much rather get a Motorola or HTC because, for the same price, I'll get a better phone than Samsung would offer me.
The main reason I buy flagship phones is for the battery life and I just keep it in power saver mode. I can go days without charging my phone. I also noticed that the charge drops off quickly from 100 to 70% but lasts a very long time between 30 and 70. It isn't until it drops below 30 that I have around 5-6 hours of charge left. I, too, charge my S21+ about 2-3 times a week and I have a lot of screen time with it daily as I use it for work.
Only times I have to turn power saver off is if I have poor reception and that seems to do the trick. If I forget to turn power saver off I'd say I have about a 30 hour battery life which could be argued as a single days charge.
I will say that the s21+ isn't worth the $1000 asking price(at time of release) but I got it for free with promotions and trade ins. And when I say free I mean free, no monthly payment plan.
I did a thorough battery test on it recently and I've only lost about 8% of the battery since it was new. I plan on running for the next year or so but I'm heavily considering dropping another battery in it to try to extend its life to the 5 year mark. I figure by the end of year 3(march will be 2 years of ownership for me) I'll have lost around 15% battery and at that point it will be economically viable to replace the battery.
I'm heavily considering getting a Google Pixel so I can run GrapheneOS but, man, do I had that camera bump on the back of them. I work in an enviorment that is not kind to electronics and I've been thrilled with the durability of the samsung. I'm concern that the camera bump on the back of the pixel will impact the durability. I put the best case avalible on all my phones and I see the Pixel camera bump as being a weak point even in the most expensive case avalible.