I'd try to get an hour of sleep more per night. It's healthier for you.

I know that if a person is used to sleeping for eight or more hours, and then begins sleeping for only six hours, his/her NREM (non-dreaming) sleep will take precedence over their REM, and they will dream less. This does not affect lucidity, because becoming lucid depends moreso on whether or not you are conditioned to question your environment.

I am not sure if NREM retains its precedence over REM if you keep sleeping for six hours over an extended period of time.