I think 1 1/2 hours deep sleep with about the same REM makes for a pretty good quality sleep.
The most deep sleep I've had is 1 hour and 37 minutes plus 149 REM. That's out of 8 hrs 37 min total sleep. I notice the higher those numbers are the better I feel during the day.
There's a function in the fitbit app; open sleep, look at sleep stages and then click on benchmark which gives the averages for other fitbit users in your age group. I need to read up on information explaining the 'benchmark' percentages. It's not clear to me, yet.
