If the ISO doesn't work, try this:
Find the girl you want to see. If you're not sure she will let you pop more than once, PM HER! Keep those questions to PM. Insist on her checking her PM.
If you're still not sure and you really want to see her, schedule. When you're just about to pop, ask her. If she says no, stop and pull out. If you lose it, that's fine. Regroup and take a break.
Explain that you want to save it for the end. If she wants to rush you to "finish", then you have a bad one. She's finished. Write an honest review. If she is a good one, you can reset when your ready. Work with her and tell her you don't want to pop early. Keep it going and work through your positions; maintaining control until the last minute when you want to finish where it pleases you.
It should be a pleasurable and fantastic nut if you've been holding on to it for some time. Especially if she knows when to stop so it doesn't happen should you be in a compromising position.
When you're time is up, look satisfied even if you're not. If she asks you: "Are you gonna see me again?" Tell her: "GO FUCK YOURSELF!" as you walk out the door and leave it open.