Lack of sleep can not be a favorable life. It will kill you faster than not eating. But not staying hydrated is even faster.
Apparently, 3 hours for you is still enough to stave off Zero.
There are some people in old age who sleep only an hour per night. Two months ago I was down to 40 minutes a day, and this amount was in steep decline. It turns out it was a calcium channel blocker doing this to me, but the main issue here is that low sleep means the immune system is not being maintained, at least in rats. After weeks of this, in rats, the immune system collapses and every bacteria in the body goes on an eating binge. Its fatal.
Five hours would be what I would consider minimum for good health, allowing time for hormone secretion etc. You can survive on one. Eight is the traditional figure, and higher than that if you have some kinds of medical conditions, including viral infection.
I normally have non-24 sleep disorder, but after restoring sleep two months ago it took about a month to kick in again. After very low sleep for a long time the circadian rhythms might reset.