Like so many others here I can relate/empathise.
Generally I find it hard to cum but more so if I'm not feeling properly relaxed. There are other factors, too. But I haven't figured out what they are yet. Sometimes I am able to cum very easily. At other times it just seems as though it doesn't matter how much I want it to happen and how hard try to make it happen it's just not going to. I can't seem to figure out what the magic bullet is. But am keen to find one, whatever it may be.
I've yet to try taking pre-punt tabs to influence my erection/performance. So I can't say whether that would help me to become more consistent or achieve a faster time to orgasm. Keen to try, though.
I haven't been punting long enough to have got myself set up with a regular yet. So I can't say whether there's one particular sp who's better at making me cum than others. In fact I'd say each punt is a bit of a trip into the unknown. But there's an element of excitement (and, as I've discovered, sometimes disappointment) about that too.
But regardless of who I've arranged to be with I always go along with the attitude that I'm there to enjoy the whole journey/experience and, as has already been said, being there with a hot/fit girl who's happy to be very intimate with me is justification enough for me to be there in the first place. If I'm able to cum too as a part of the experience then it's just the icing on the cake. Pun intended.