One of the ways I judge is by how my body feels. If I sit too long then I start to seize up, and if I don't walk each day then my legs ache. If you look at a day a lot of people will sit down after dinner and just watch TV. If you go to bed at 10 and ate dinner at 5 then you spent 5 hours watching television. So, I would say you are being productive instead of just sitting there. Are you enjoying yourself?
My time varies a lot depending on what else is happening in my life and I work in bits. My machine stays set up most of the time and I might sit down for just 10 minutes sometimes between other jobs or I might sew for an hour. Each day is different and I have never added up how much time I sew. I had a deadline a month ago and did do a lot more to reach it in time.