For me, it's very much cyclical: when there is a project going, there are so many people counting on you that pretty much every minute counts, and the cost of mistakes is always high. It's during these times that time management skill is critical and you need people on the team who's job is to manage everybody's time and make sure things gets done, but even with that, the long hours are unavoidable. I don't think it's something to brag about, it's the nature of the job.
But when there is no project going, it feels like there is really not much to do all day, sometimes even the task of finding things to do is a struggle, so you do whatever you want until the next project starts.