I think 80% is already a too much in practice. It also depends on the work. If it needs a lot of concentration 80% is just not realistic. If there is some varie

I think 80% is already a too much in practice. It also depends on the work. If it needs a lot of concentration 80% is just not realistic. If there is some variety, e.g., sometimes people come to ask you something, it becomes easier. But then there is also non-productive time that your brain needs to switch tasks. There are at my job maybe some people who are around 80% but they seem to be combining producing much code in little time by producing code that has a relatively high count of bugs so that may not be that productive either. All those people who want to tell us that they are working much more or that we should be working more are probably not very realistic. E.g., have they have not measured the time that they spend on pouring tea or similar activities.