I used to buy the "got name " brands of instant water heaters.
The first one in my master bedroom lasted many years ( can't remember the name, probably 707 . But I remember got Union Jack on the box. ) More than 10 years. When it went kaput, I replaced with same brand but it died within a couple of years! Changed to another brand (IIRC Joven ) also didn't last long. Fed up bought cheaper one Champs. Liked that one. But lasted several years ( more than the previous heater). Replaced with another Champs
All that in less than 30 years.
In common toilet, IIRC changed only once. First 17 years, it was underutilised. When it gave up, Changed to Panasonic dunno how many years ago. ( more than 5 years ago)