Hmm,
to begin with, the kind of loving I give cannot even be sqeezed into 30 mins..
Absolute minimum is one hour to get the mood right, to get a feel for eachother.. to kiss !
Now, if in that one hour you have the endurance and wherewhitall to reach the heights 2, 3, 5 times, good for you....
However, I believe it is so much more satisfying, so much more enjoyable to tease and seduce and take you to the brink and hold you there for an extended time.. repeatedly... and then when you Do reach your heights it will be unparalelled by any "pedestrian" experiences...
Ah, it's just my humble opinion xxx
Oh, yes, and lets not forget about the "after-care"... the hugs and kisses and the lingering intimacy...