Launch day 12 Pro user.
My phone has been in a case since around 2 minutes after it left the box.
ESR clear case until the Apple leather ones launched. It lived in the leather Apple case for just over a year and was only removed to replace with an Apple silicone case, no cleaning.
Removed from that after 7-8 months and went back in the original leather case until using a wired charger that wouldn’t fit with the case on, yesterday afternoon. Again no removing for cleaning.
I did check the phone over whilst out of the case yesterday and found it to be in pristine condition, other than 2 very small marks around the lightning connector.
So almost 2.5 years of not very careful usage with my first stainless steel iPhone and I’d say it’s held up pretty well using the Apple cases.