The worse day to not be at work is Monday
As a freelancer, I, in theory, am able to pick which days I work, and I often have to do so, to make sure I get family stuff done, such as doctors appointments, and such. When I take family trips, I have always made sure to be back by Sunday night, mostly because I like to be back before the week begins. Plus, if somethiing came in over the weekend, I would still have time to get to it before Monday.
A couple weeks ago I had a conflict where I couldn’t be back from a trip before Monday afternoon, late. I figured if I let all my clients know, and checked email, I would be fine. This was not the case. Even though Monday is often slow, there are things that come in that have to be up by Monday, so I found, once I got home, that I had to stay up until 2am Tuesday morning to make sure I had gotten all the work done that people had asked to have done that day.
So, despite the savings I got from flying on a Monday, I think next time I will stick with my rule of coming back home by Sunday night.