Only done it once, but I think it's is a race of two halves - before and after the summit of the second Peak (Whernside). Stay well within your comfort zone before then, then asses how you feel, as you still have about 45% of the race time left (assuming a consistent run).

Better to listen to your body than think too much about split times. You know approximately how many hours you'll be out there for, so just think about that. If you feel suitably fresh at the top of Whernside then think about changing gear, but if you're starting to feel uncomfortable then give yourself an easy 30 minutes or so before the final climb starts.

If you've done the race before I think it's too tempting to set off trying to get ahead of your early split times with the consequence of suffering too soon and getting a slower time by the finish. I've spoken to a few people who've done that.