Normally a 3.5 to 4.5 i guess.
One phone, before I had a case on it, and only 2 days I smashed camera lens cover after getting out the car. Thats pretty rare though.
I normally use full surround cases but ones that i can slip into my pocket easy, nothing that will bind or be bulky. I drop phone every once in a while but don't do damage.
My wifes phones normally die from dropping or water damage. (Dropping in bucket of water etc). So normally replaced when broken.