When I sleep say 4 hours then stay wake for 3 hours, sleep again 4 hours. (Note, I haven't really been keeping track of my sleep but that's more or less how it goes), I'll lucid dream, more so I'll see myself laying down on my bed, with the vibrations going, ready to astral project. I don't feel like I lost energy, actually yesterday I slept from about 2pm to 5pm then from about 7pm to 1am, finally I completed the night sleeping from about 4 am to about 6:30 am . I don't feel like I've lost energy, but that's just me probably ;)
Last time I tried this I remember it also being successful at waking up lucid inside the experience.
First sleeping session I astral projected which I recall, 2nd one I didn't even remember, third one was a lucid dream that I successfully recalled.
Today's a school day, I'll probably sleep early wake up around 1 am then spend 2 hours awake, then sleep the rest of the night. Sweet dreams :) hope this helps!