Actually, no. I've found that sex always gets better with time. The first time it may be good, but is usually just okay. But as you get to know each other better, and deepen your feelings for each other, it gets better and better and better. Sex without love, or at least friendship and respect, is a hollow experience.
So, the "just once" thing has no appeal for me.
On the other hand, the old "I'd like to chain her in my basement and fuck her every day for a year" feeling comes along quite often.
I must see a half dozen or more women a day that I'd like to have a "just once" experience with because their yoga pants fit ohh so right, the clerk at the grocery store with the cute smile or the leggy young mom walking with a stroller.
But for someone I actually know, my wife has a married friend who lives out of town and occasionally stays with us. She's smart, funny, petite and fun to be with. The last few times she's been her she has become comfortable enough to lounge around in her pajamas and is clearly braless when she walks with the jiggle of her tits.
But what drives me crazy is her beautiful ass. If I could do it 'just once" I'd like her to let me lift her skirt up, bent her over a chair and do her doggy style. That would well be worth a "just once" experience.