I think it depends how strong a climber you are. If, like me, you are decidely average then I would ride at your own pace from the start and not worry about it too much. I haven't done the 312 but I would imagine the level is fairly high with most riders not really getting in the way unless you are way above average.

Do you know what start pen you are in? That can make a big difference too on these big events. If you are starting around midfield or higher then you already have a huge head start on those at the back. You may need to pay more attention to the early pace if you are in a late start pen.

312 km is also the sort of distance where you can seriously suffer/fail if you do overcook it early on.