You can fit 750meg data, mode 2 on a 74min disc (or really close). But when you burn mode 2 for the first time, zip down a bunch of your REALLY critical files (tax documents, passwords, game save files, porn movies). Then burn it to disk as a bunch of individual .zip files.
Now, for the fun part, run a 'test' using winzip/winrar on all your burned files. If you have a REALLY good burner, not a single one will pop a crc error. If you have a medocre/good burner, only half of them will be wasted.
(made this mistake, with a bunch of old class notes, when I first got my burner ....doh!)