A simple approach is to just be aware of how close you are to cumming. There is a point of no return(PNR), a point of getting close to no return (GCNR), and cruising altitude(CA). Easy enough, when you even get anywhere close to GCNR, stop or slow down, get back to CA where you feel you are in no danger of cumming. It is best if you tell your partner in advance so when you have to stop she won’t get all mad. A technique to continue to please her without overstimulating her is to be on top, push in as deep as you can, and then just rock slowly on top of her with out moving in and out. The rocking will continue to stimulate her without a lot of sliding which would set you off. You can switch positions and take your time, giving yourself time to come down in your excitement level. If you need to pull out completely, and give her oral or manual stimulation until you bring your excitement level back down to CA. After a lot of practice, you will get real good at controlling your level of arousal. The advanced level (my favorite) is to stay just at GCNR for a couple of hours….HEAVENLY!!! I will tell my wife to slow down, or go softly when she is sucking me, and then she knows I am close to cumming. This is a huge turn-on for her and many times she will go harder and diliberately try to suck me over the edge!
I find that initially there will be a tendency to go racing over the edge of the orgasm cliff, but if I slow it down and stay at CA for a while, sensitivity drops slightly and then I have much more control. I have never had problems with lasting a long time, because as a kid I would love to jerk off for hours, practicing the same techniques I’ve mentioned above….just because I loved how it felt and wanted it to last as long as posssible.
Good luck!!