I have 30 hours workweek and work 5x6, for the last 7 years. I also negotiated that I can leave at noon, and work the remaining hours, from where ever I am, whe

I have 30 hours workweek and work 5x6, for the last 7 years. I also negotiated that I can leave at noon, and work the remaining hours, from where ever I am, when there is need (e.g. when I need to answer crucial things at evenings, weekends etc., which happens maybe once in a month). It is very good, I can spend more time with my son. I can go running when there is still sunlight outside. The problem is I could not go back to an 8 hour day. I don't abuse this deal: When I really want to get things finished, or when there's something critical, of course it happens that I am still at work Friday 4PM. It works the other way, too: When there's something critical at home (and no planned interaction at work), I may not show up at all, and it is Ok.