Taiyo yuden only make -R DL discs, they are not the easiest to find and burner firmware support isn't as good. All my 360 backups are on Verbatim +R DL with the booktype set to dvd-rom, all where burnt with either a pioneer or a lite-on dvd burner and even games I haven't played for sometime still spin up fine. I put my backup of table tennis in after not playing for about a year and that spun up fine.
When you say "(unless i work with them for about half and hour)." can you explain that a bit more? do you mean if you leave the box on for Â½ before then if works?
Also how are you storing the backups?