I am 77.56164384 years old and often stay up until 4-5:00AM. -- But, then I wake up at 8-10:20 AM. and often take a nap after a longer than usual jog, usually in the late afternoon, but maybe morning or some other time of the day. That means, I guess, I am living a suboptimal lifestyle. But once I get tied up with computer - I might as well keep going as long as I can until I really feel like sleeping.
I constantly check my ECG on my Apple Watch Ultra, and very hard runs get it all upset and I have to take it easy for two days, sometimes. This is the age when you have to start getting cautious about pushing yourself too hard.
So that watch ECG - yes I really need it.
And by the way, it tells me that long naps during the day are NOT good for the heart.