I switch phones when they become unusable, so about 4 years in my experience. That's plenty for me, especially since I buy older (cheaper) models. Also, I'm rough on my phones so I outfit them with heavy-duty cases from day one.

My previous phone was a LG Stylo 3. It lasted 5 years, albeit with greatly decreased battery capacity. I was just thinking of ordering a replacement battery when it suddenly bricked itself while charging... first time I ever lost a phone unexpectedly. Before it I had a Samsung Note 2 - its charging port started failing but I still managed to backup everything by hotwiring the battery.

I really wish we could repair phones more easily and cost-effectively. I just can't accept that something that costs ~500 CAD is "temporary", technological changes be damned.