That's exactly it (except that k=5 is not reasonable). The REM periods get longer and longer as you sleep; that is, the "cycles" do not have the same period. E

That's exactly it (except that k=5 is not reasonable). The REM periods get longer and longer as you sleep; that is, the "cycles" do not have the same period. Edit: also, k=0 is valid, and what most people have been advocating here (as 20 minutes).