I'm a very busy student who can only sleep 4 hours and 30 minutes per day.

During the semester, I can't sleep earlier than 1:45 am and cannot wake up after 6:15. Fortunately the 4.5 hours fits in the 90 minute REM cycle.

Since it's winter vacation right now, which means I can sleep more, I'm doing this:

1. Wake up at 6:15, write down dreams(doesn't matter if I couldn't remember anything). Sleep again if I'm tired.
2. Wake up at 7:15, if I can remember dreams, write them down, and sleep again if I'm still tired.
3. Wake up at 8:15 and do the same.
4. Repeat this every hour until I don't want to sleep anymore.

Usually it ends up like this:

I remember dreams at 6:15 and 9:15. I sleep without alarms from here, wake up naturally at around 12:30, remembering some more. Which makes me have 2~4 dreams in my journal.

I can do this because it's winter vacation but when the semester starts, I'll have to wake up at 6:15 whether or not I remember any dreams.

Would LDing and remembering dreams be possible even with sleeping 4.5 hours every day?