I kinda know based on if my code is really long, undocumented, or has poorly named identifiers. I also know when other people look at it for pull requests for me. If it doesn't make sense to someone else on my project without a ton of explanation, then it's probably not readable or maintainable

We don't have to work 8 hrs but I usually do. I think the number of hours and what feels like too much depends on what you are doing. 8 hrs of meetings, documentation, or tedious codingand I'll be fried and exhausted. 8 hours of solving interesting problems and I am usually hungry for more.