How many of your iPhones made it out alive/fully functioning by the time you were done with them? I am in-general gentle with mine, but came to the realization that only my 5s (barely) was fully useable by the time I let it go. I generally only switch when there's something terrible going on with the last one:
-3Gs: About two years in it quit charging... Unless it was turned off. It also wouldn't sync (in the exact version BEFORE you could do so over Wifi.) The power button eventually broke
-4: Home button quit working half the time, volume buttons didn't have an effect after a couple years (collapsed internally)
-5s: Still works fine but... A month after my three year supply of bumper covers wore out, I dropped it and the whole aluminum frame bent, partly detaching the screen. Yet, nothing else was affected. Never liked how fragile the aluminum frame was vs. the 4
-7 : This one's still good, but I got it used last week. Perfect condition. Fingers crossed
-3Gs: About two years in it quit charging... Unless it was turned off. It also wouldn't sync (in the exact version BEFORE you could do so over Wifi.) The power button eventually broke
-4: Home button quit working half the time, volume buttons didn't have an effect after a couple years (collapsed internally)
-5s: Still works fine but... A month after my three year supply of bumper covers wore out, I dropped it and the whole aluminum frame bent, partly detaching the screen. Yet, nothing else was affected. Never liked how fragile the aluminum frame was vs. the 4
-7 : This one's still good, but I got it used last week. Perfect condition. Fingers crossed