i understand that you need sleep to function. i posit that it might be the case that you need *less* sleep for the same amount of function (energy, alertness), if physical activity was part of your day. i know it's the case for me that there are 3 factors i can tune and a couple i can't that affect how much sleep a "rested" me needs (not nodding off at work, in good spirits by default).
- amount of intoxicants i consume. alcohol is not the worst offender here. can make a difference of up to +2 hours in my "how long do i sleep before i wake up naturally" number
- getting some exercise: at about 45 minutes, i take an hour off needed sleep to feel right. it also serves similar to a cup of coffee--doing it at 4am will rarely leave me able to sleep before 6am.
both lead to more sleep needed, or less good sleep being gotten in the same amount of time.
i am a sounds sleeper, so the following statement doesn't apply. but perhaps it is relevant to your situation, even if you've never realized it? are you getting good sleep? do you have apnea, do you have a dark room, a comfy relaxing bed, a quiet place? could be that moving off the main street would be all it takes for 6 hours of sleep to feel as good as 8.