Evidently, the type of black O-ring I’ve been using isn’t as good as the red Silicone O-rings.
Although I can get the O-rings to stay for 1/2 to 1 hour if everything is clean and oil-free and I don’t stress them, the silicone rings tend not to slip. This may make it possible to sleep longer with just an O-ring as a retainer.
For now, I’ve ordered the red O-Rings in two sizes, 5/8 and 7/8 inch. I’ll report back after testing the new O-rings.
Here’s a tip (no pun intended). I found a non-standard O-ring stocked by pinball machine parts supply houses. it has a 3/4″ inner diameter and is 1/4″ cross section. Comes in black and white. The thicker cross section grips better and pinches less. You can also get a stainless steel pinball to place between it and your glans, for added tension. I sleep with it and it stays on all night. I used the ball with it during daytime.