One or two per phone.

iPhone 6s I had two because one ended up disintegrating. 8+ had two because the rubber ended up wearing out on the first one. 11 Pro only one because I had it for less than a year. Current 15 Pro I have one and no current plans to buy another one. It’s thick ish and has colored sides with a clear back so I can actually see my phone and see what I paid for lol.

The idea of having more cases is cool but knowing myself I’d get lazy about changing them and end up using one.

Have had the Apple Watch for 4 years and it’s safe to say that the main ones I remember is the sleep tracking, heart rate and steps being more easy to access.

Oh and the main one being how long the battery life is!