Well i'm a noob to DVD burning, but I have burned 50 DVD's in the past 2 weeks since I got my DVD burner so I've learned a lot the past two weeks.
I use DVD decrypter for the occasional movie that, even if stripped, still will end up being compressed down to 50-60%, which many people say is a noticeable loss in quality. From what I read, rule of thumb is anything near and above 70% is generally unnoticeable, so that's the standard that I adopted without actually testing that theory.
I backed up casino today, and the movie itself is already 7+ gigs. If you want to get it to fit on one DVD you need to compress it almost 50%, which by the 70% standard is very unacceptable, so I use dvd decrypter + dvdfab (tutorial can be found on mrbass or doom9) to split it and create the movie on 2 dvd's instead.