Don't have any hard science to back me up as to the sleep-evolution thing, but I have the same experience. Unless I do something dumb like pull an all-nighter during the summer, or have my kids starve me of sleep due to kiddie sicknesses for a few days, but those are exceptional circumstances. Then at some point I need to make it up, and do, at the first opportunity. Then it is naturally back to the regular rhythm.
Unless you have gone from 7-9 hours to, say 3 hours - I would consider that extreme and worthy of perhaps some digging - somewhat shorter nights are okay. Are you still rested and otherwise good for the day??
I have a mantra that I have spouted for years... "If I eat right, I feel right. If I feel right, I exercise right. If I exercise right, I think right. If I think right, I eat right..." Phil-SC