Spinning the wheel is close to a once-in-a-lifetime experience, so I'd always lean toward spinning again, even at 70 cents. With 75, I'd stay.
I've noticed Drew lately is pointing out where the needed amounts are on the wheel (like with a 70, he'll say "the 30 is over here") ... nothing wrong with that, assuming you could finesse it around. But I think you have to just give a big spin and hope for the best.
The odds of you winning staying with the 70 is about 21%, or about a fifth. Odds with you winning spinning again is about 16.7%, or about a sixth. Although you are going against the odds, I am not that angry, because even spinning a 5 would increase your chances by 5%, and it gets exponentially better. So if you want to do it, by all means.
(Just want to make sure you know the odds. I know for a rule of thumb that you are P1 you spin on 65 and under inclusive. P2 should spin if 50 and under inclusive, and stay iff P2 is a better position than P1 and the value is at least 55.)
Sources: An Excel spreadsheet I made in about 15 minutes and some random article I can't remember the name of.
Self Edit: Could someone actually do a tally of the number of times a number was spun on?