Instead of homocidal intentions, think of that extra time as cultivating a relationship with a potential returning client.
If you don’t want to see the guy again, you can tactfully tell him when his time is up.
But if you like the guy and want him to repeat, spend a little extra time to get to know each other. If the guy is like me, he will want all the more to come back. Granted, two and a half hours is excessive for a one hour date, but an extra 15-30 minutes should be beneficial.
If he’s a return customer that starts to overstay his welcome, he should be receptive to a gentle nudge that time is up.
I think most guys want to please their companions. Those that don’t...those are the guys you don’t want to see again.