Mine is almost always constant, if I go 5-8 hours with out a nap I have accomplished something! I am The Sleeper! What little energy I have just disappears and I need to lay down or fall down.
It`s not like I spend any real time standing anyway, but when I start to lean sitting in a chair it`s nap time. Sometimes I don`t even sleep, I just need to be horizontal.
On the bright side? it`s better than dead!