Sort of. I sleep for 9 hours if I've been up for more than about 14 hours prior and there's no alarm. If I've been awake for more than 24 hours it goes up to 12hrs.

If I've had several drinks (alcohol), I never sleep for 9 hrs, it's always less, but I haven't tracked post-alcohol sleep times closely enough to notice if it's still a multiple of 3.

However, I can also do 6 hrs or 3 hrs, and I don't feel groggy but I'll get tired sooner the next night. Not adhering to a multiple of 3 hrs (rem cycles I assume), or reasonably close to that, ends up badly.

What I really need is an alarm hooked up to a primitive EEG so that it can start the clock when I fall asleep, and set off an alarm after a programmable number of minutes. That way I could sleep for 6 hrs without ever being groggy. But even the cheapest EEG stuff I've seen connectable to a computer is not cheap.