I would always back up my best ds game save file as I don't want to lose it due to physical damage, corruption, or go without time based events from dry internal battery. I was also wondering if the same thing could happen to my save file on an r4 card. Would I be able to retrieve it? Also, if internal battery runs dry on the original ds game and I back it up, will the it be the same if I put the save file on the r4, or am I able to use time based events again.