I've mixed together several of my favorites for a two-hour sleep file that gradually tapers off to nothing by the end.

EMGs Erotic Dreams

Major Pixel's Slow - Help Sleeping / Suck My Sweaty Jock / Savor My Cum

Jack Drago's Cosmic Orgasm

achummer's Yellow Arousal

devildong77's Pumped Penis v.2

000's Night Time Cock Worship

kablooie's Binaural Delta Deepener