I also tend to run most of my loops during sleep, but I’ll also run loops during the day, when time permits.
I tend to interleave Major programs and Ultimas. I’ll have Paragon close to the start of my sleep cycle. Later when I’m fully in REM maybe a loop or two of Stark or RM.
Results are not a problem, sometimes it looks like nothing is going on but then I’ll reflect on something like how my style of writing/discussion on the forum has changed and the insights I’ve been having and realize these are all connected to the topics the subliminals touch on.
I don’t particularly find it makes sleep any more difficult, but i do find periodically I’ll wake up halfway through the night and not want to run the subs for the remainder of the night. Like others have said it makes sense to give your brain time to process especially when it feels like things are backed up. Also, if u listen during sleep, comfortable headphones are a must!