It's a generalization, but for an Ironman (especially a very hilly IM), my motto has been "better to have it and not need it than need it and not have it." But I'm an MOP completer.

I have to admit, having mapped in Strava, I've done a lot of hilly races and never really worried about cutoffs. Given my training rides to date with lots of climbing, my mph is looking a lot like an 8 hour bike split, which I can't wrap my head around. First time in a long time I've been a little freaked about beating the cutoffs.