I have a spare iPhone 6 Plus that I use to allow little kids to play games and watch movies on. I've been having battery issues and took it into Apple Genius Bar. They said I qualify for a replacement, but that they were backed up on iPhone 6 Plus batteries until sometime in March. This phone will shut off not even after an hour of use and is very very laggy. I was considering taking it back in to Aplle Genius, but was wondering if it's unreasonable to ask for a replacement? The AppleCare on this has already expired. Thoughts?