that´s no more a point with DVD SP.
I´ve never seen a single menu, that will flood the 1GB-limit, and if you´ll have more menus, so the amount will hit the 1GB-limt DVDSP will swap these menus into the next VTSM.
according to max. duration on DVD-5, I would never put more than 110-120min of video on DVD-5, and they should have a 2-pass VBR-encoding.
this calculation includes that you´ll use 1 dolby digital audio-stream@192kbit/s.
so you´ll have an average-bitrate at about 4.8-5.2MBit/s.