I put in forty hours a week as per my employment contract states. If I'm more or less productive is irrelevant to the amount of time I have to take care of myself or my family.
If I have a productive day, I sign off between 4-5 PM. If I have a non-productive day, I sign off between 4-5 PM.
If I happen to be more productive it does not mean I get more hours to do stuff in my personal time / get more personal time.
Because I am more productive when working from home, I can easily get the job done in half the time. This means that my manager is happy, and I sign off after lunch and have the rest of the day for myself. That's also why I always try to schedule meetings no later than 1pm.
If I have a productive day, I sign off between 4-5 PM. If I have a non-productive day, I sign off between 4-5 PM.
If I happen to be more productive it does not mean I get more hours to do stuff in my personal time / get more personal time.