Can I survive on even less sleep?

Tell me if this makes sense.

I'm thinking about cutting down on my sleep.  Here's my rationale. 

I go to sleep sometime between 11:30 and midnight every night. 

I wake up sometime between 5:00 and 5:30 every morning.  Sometimes a little earlier.  

This routine does not vary regardless of vacation schedules and weekends.  I never use my Saturdays to "catch up on my sleep."

This means that I average about five hours of sleep a night.

But I am almost never tired when I go to bed, and I...