Has anyone had any experience with keeping a smaller iPhone (4s or 5) as a backup for the Plus for use while running, cycling or at the gym? I've been leaning towards using a 6 as my sole phone since I run or cycle every day, but started thinking I may be better off with a smaller, cheaper phone for those activities anyway. The 6 and the Plus work, but neither are ideal. My concern is swapping my SIM back and forth between the two phones on a daily basis. I've only swapped when upgrading each year, so I'm not sure if daily swapping poses any problems I should be aware of. Thanks for the help.