Only three answers so I actually read them instead of skimming them (most people incorrectly use "scan." Scan means to examine closely, line by line, point by point, letter by letter if need be.) Had someone else given you a good answer, I would have gone on. I have weeks of unopened email that the Yamster would not let me open, now I am playing ketchup.
You fit the term "healthy insomniac." I have gone for months on three hours a night with four to six fifteen minute to half an hour naps scattered throughout the day. Unfortunately, right now I seem to be on the opposite side. Short version: had a female stalker that tried to kill me twice, but it was what she did when she was NOT violent that left me with pretty severe PTSD. Nothing ever bothered me before, but looking back, I experienced a severe trauma that lasted for close to two years. Medication was recently prescribed for a condition I kept saying I did not have (anxiety) but family talked me into trying it. Now I am trying to recover from the trauma of medication that was vastly unneeded. And I am left still dealing with still not having anxiety. ;-}
But back to. Unless you are atypical, you go through sleep cycles of 90 minutes. If you cannot get at least three contiguous cycles, you need to set an alarm so that you will complete one or two full cycles. If you have ever been awakened and felt worse than when you went to sleep or felt as though you were in a dream, it was because you were awakened in the midst of a sleep cycle. If you cannot get even one full cycle and you are sleepy, you might be better off staying awake for a while longer.
Can you power nap? I can, literally, go to sleep, be dreaming and wake up on my own in three minutes, feeling greatly refreshed. I did not know I could do that until I was about 30, and then discovered it accidentally. But if pressed, I can go for 2 or 3 days with no sleep at all, then 5 minutes sleep about every hour will keep me going for anywhere from a couple of days more to as many as five days. Then I crash for 10 to 12 hours. At least I could do that when I was in my thirties. Once, in an emergency situation, I worked for almost 60 hours straight operating some dangerous equipment and had no problem staying alert. Had I ever had any doubts, emergency or not, I would have shut it down and then shut me down for a while.
Supposedly you do not "catch up" on missed sleep. Instead, what happens is you go more quickly through the lighter stages of sleep and spend longer in "REM" sleep, the deepest stage. (REM is Rapid Eye Movement.)
Supposedly you cannot dream when you are not in REM stage, so my dreaming and waking up in less than 180 seconds indicates I almost instantly went from awake to REM and back to awake. But I suspect that the belief you dream only in REM sleep one day will be proven false. Could visual, auditory or tactile hallucinations be nothing more than dreaming when you are awake?
But though it is claimed you do not catch up on sleep, as far as nutritional benefit, does it matter if you dissolve a vitamin tablet in water and drink it, or take it and drink the water later? To me, getting a higher percent REM sleep is getting the same amount of sleep, just getting it concentrated. There have been enough studies done that would leave me believing that going even a few months occasionally less sleep would cause no harm, as long as you feel rested and refreshed. Each person is different, but I think you have nothing to worry about.