In my humble opinion, although multiples are certainly nothing to sneeze at, I think too many people, too often put too much focus on them. Relax, savour and enjoy just simply BEING together, and the PLEASURE, and enjoy the outcome whether it be ONE or several.
I'd also like to add, that if SHE feels like he's completely knocking himself out trying to get her off, IN HER HEAD, it can be a rather COUNTER PRODUCTIVE manouver. Too much pressure/expectations = NO orgasm, OR a difficult orgasm.
Am I making sense??