wank about 30 mins before the punt that way youll last longer!
If you're intent on saving it up you may find yourself coming earlier than you expect, so make sure you agree beforehand that you can come more than once.
It's about knowing your own body. If you know that holding out for week will result in you cumming too soon with little hope of recharging, I would only start holding off about 24-48 hours (the amount depends on how you think your body will respond) before the punt. If you think you will have the stamina to hold off before cumming when you want as many times as you want, then hold out from now. Good Luck
At least 2 days. Having a wank on the day has saved me a fortune in the past because the desire suddenly recedes and I've often cancelled planned meets.
I normally do 4 hour+ sessions now so save it up for a week, all the better to drown the young lady in question with on pop 1.