Tired

I'm tired. Much more tired than I think I should be given I took my scheduled naps today (10, 2, 7). I felt fine during the day, but then did fall asleep in bed while my wife was reading to me just before midnight. Managed to kick myself out of bed and do a bit of reading, but my eyelids feel quite heavy and I'm going to take a short nap. From past experience, I know I need to set a backup alarm and keep the alarm itself across the room so I have to get up. I don't want to be miserable, but I really want to restrict myself to never sleep longer than 3 hours max again for a while.

I wonder if this extra fatigue would be different if I'd gotten 2-3 hours of core sleep at some point last night rather than only 30 minute naps. Is 2 hours of sleep the critical difference? I think for the next while I'll make sure I always have some core sleep at night and see if I have extreme fatigue moments like this one again and with what frequency.