Maybe I've been lucky to date but since my 4s days -2012-actually also my Blackberry before that...- I've always charged overnight, every night on all phones ( and tablets).
The battery wear & life on the 4s was good for 3 years and it was actually screen size & storage issues that pushed us to upgrade. My 6 was a battery disaster from the get-go but here is the islands we simply don't have the comprehensive customer support bigger countries and cultures have gotten used to. The 6+ for my wife provided also 3 years but again, it was camera issues which led to replacement with her 8+. I had replaced my 6 which had numerous problems with 7+ which gave 3 years yeoman service. The battery had weakened ( less 'staying power') and was at 91% Health so I had it replaced, and the phone is now an 'operational spare' or for use of family or visiting guests on its own Apple ID & account. My wifes 8+ is approaching 2 years and just went to 98 % Battery Health a week ago. I couldnt say if there is a 99% or what the increments are as its really a non-concern. My 8+ being 5 months is a solid 100%.
Devices are charged if & when needed during the day, and overnight. Since her 8+ and our first exposure to QI, wireless has been the mainstay of all iPhone charging, cable charge for the iPads of course. Last few years we have used a 'Griffin Dual USB 12W charging block at each bedside, to power cable ( cloth covered,) to lightning connector for iPad, and to USB A for QI charging discs. Cabling is Griffin aa well.
As an aside, ( I can't really see it as being a factor, good OR bad) is that our nation's electricity is supplied at 50 cycle, 110V as opposed to the 60 cycle 120V used elsewhere. That can affect many things but electronics seem to 'know' and either work or do not work. Motors & things like clocks are another story though.
The climate here is tropical, generally mid 80's to low 90's daily year round, and only the bedroom is air conditioned to about mid to high 70's at night. For those outside the USA, temps in C here are up to 34 daytime ( average 30ish) and about 27 or so overnight. Definitely in the upper range an iPhone can be expected to see, with the exception of possibly Middle East or India
I simply say "so far so good"