Are there any negative effects of having a somewhat irregular sleep schedule? Some nights I sleep 6 hours one night, 9 the next, 6 the next, ect..

I generally feel good and it opens up more hours in my schedule than when I slept 9 hours per night. After sleeping 9 hours, the following night I'll have a cup of tea or some diet pop in the evening and be good to go till midnight or a little later.

Is there anything bad about this?