As long as the games are burnt well, the DC doesn't seem to mind backups too much. It is built well enough to take a pounding of extended periods, so backups shouldn't hurt it at all.
As for the game disc that stopped working, I'd imagine that the CD is slightly warped. You may not be able to see this with the naked eye, m8. When you put the CD into the drive spindel in your DC, give the sides a LITTLE flex, not much. Add a bit of gentle pressure to the opposite sides of the CD as if you were puching it onto the Spindel a bit harder than normal. You may find this cures yuor problem. If so, just pop it into a CDwriter and reburn the disc.
