Ask HN: How many actual on desktop hours?

I use an app called Rize to track my on desktop activity as well as classify it. I used to use RescueTime but their UI is from 1998 so I made the change and I like it. I average around 10 hours so far but want to up my game in terms of focused work on desktop. Around 70% of this is full focus work, either design, coding or marketing stuff with my startup. I am curious if people who average more than 12 hours are able to keep it up and have tips to achieve that.