Fantasy is great - it changes things up for us. I sometimes fantasize when I'm with someone. When with the wife, sometimes I will close my eyes and imagine that the sensations moving through my boner are from sliding my hard-on between some guys ass cheeks, or that he's sucking my cock ever so softly. When I've been with guys, I might imagine that I'm titty-fucking my wife and I'm blasting my hot load of jizz all over her.
This is why guys like a blow job or hand job; or to titty fuck, or sliding their cock between butt cheeks. It's the difference of texture that creates different sensations, as much as it is doing something other than straight-on fucking.
Remember the first time you went commando - the feelings generated on your cock, the way your balls swung against the material? Lord, my pecker was prodding against the pant leg immediately!
Years ago, I bought a pair of sateen and a pair of real silk briefs. The feel of the silk - smooth and cool on the head of my dick was an instant turn-on. Boner heaven! The sateen ones had an even smoother feel to them. Not only did I get a hard-on the minute I slipped them on, I blew a load like I hadn't cum in a month.
It's why I sometimes like to lie on my stomach and thrust my cock across the cotton sheet of my bed,
or why I enjoy teasing and stroking on my stiffy through my pants.
And, why, once in a while I love getting out one of my masturbation sleeves to stroke my cock, or wedge it between a couple of pillows and thrust into it.
Or jacking off outside with the warm sun on my body and a little breeze tickling across my nuts.
It's all about changing things up to get the most enjoyment out of the activity and the orgasm.