I’ve been on the iUP since the 7 came out, and have been caseless for much longer. The only requirements for the return phone is that it: powers on, functions properly, and has no chips, cracks, or breaks in the glass. Anything besides this such as dents and scratches aren’t a problem when returning the phone. The worst case when returning the phone is being charged $99 for repairs if the phone is extremely damaged.
This was one of the big draws of the iUP for me, as I always felt bad going careless, as I knew it was hurting my resale value. This isn’t a consideration with the iUP, and gives me some peace of mind