Apple Photos/iCloud multiple devices & eventual overlapping IMG name?

Hey everyone. I've finally started to investigate Apple Photos as my trusted source of backing up my photos. My local backup just looks for new photos from the Photos folder and backs them up. Anyways, I've been wondering lately how Photos handles that with using multiple devices, you're eventually going to overlap IMG names. How does that work? I mean, if you buy a new iPhone every 2 years, you'll have overlapping IMG names every two years assuming you start off at IMG_0000, compounded by however many devices your replace (i.e. both my wife's phone and mine).

Has anyone already experienced this?