You can adjust how it is compressing the DVD file. The bigger the KB you set for the end file, the longer it will take actually. So, if you click the Apple TV preset on the drawer panel, it will automatically make it an h.264 encoded .mp4 file at 2500 KByte/s...or a very large file. Great quality, but big, and long to encode.
Set it to encode in non-h.264 (x.264) .mp4 with about 1200 - 1400 KByte /S or KBit/s whatever it is. And the encode will go much faster, and still look pretty nice.
Brian