Your problem has nothing to do with the drive.
How many hours that can be burned depends on the type of DVD that you use and could also depend on the software you use. Maybe you're using freeware and you can't burn more than 3 hours unless you buy the software.
Also, the quality of the movie being burned would affect burn time.
If you burn at 480i you can probably get 6 hours; if you burn at 720p or 1080p you'll probably get 2-3 hours.
You might also want to buy blank DVD media that's labeled "DS SL" (Double-Sided Single-Layer); they have the capacity of 9.4 GB.