Vote tonight, but reporters reckon he will win it. This would mean at least one more year of the guy.
It won't. If he (as looks likely) holds on today, then we look to the results of the by-elections later this month. If those are as bad as they're currently looking (and I suspect they'd get worse if Boris hangs on by the skin of his teeth), then it doesn't matter what the current rules say. The 1922 will change the rules if they need to. Or Boris will be taken to a private, dark room and given a stern talking to and he'll reluctantly resign (Theresa May v2.0). If I was a betting man, I'd put my house on it that he doesn't last another 12 months even if he wins today (assuming it's a narrow win).