Many DVD players have problems if the birate is to low, they get jerky or even stop. A lot of advice around the place is to keep the bitrate over about 3000. Dunno how accurate this is, I try and keep over 6000kbps.

Size wise, 3 movies, 1.5 hours each is 4.5 hours.

TMPGEnc estimates a bitrate of 1850kbps will run roughly 160minutes (2 hours 40min on a single layer DVD) but this is a reduced video size of 352x288, slightly more than 1/2 of standard DVD frame size, much less than standard TV.

Based on that you could probably get three movies onto a dual layer DVD (in DVD compliant format), but I reckon it would be pretty poor quality.

Just put each movie on a seperate single layer DVD, at roughly 30c a unit, against $6 for a dual layer DVD, makes more sense.