I did this this Winter. The year before I tried dealing with Winter depression by remaining sober, but four day weeks seemed to work better. Granted where I'm at in my life has varied quite a bit between those two years

Employer prefers this arrangement. I'm at a small company, if someone leaves for a week.. it's hard, because a client may call & you're the person who can handle their issue an order of magnitude faster than anyone else

When you take a week off, it's hard to readjust to being back. & now you've blown most of your vacation time, so there's nothing to look forward to. Whereas I spent every week feeling a day fresher than everyone else (I took Mondays off, not Fridays). Additionally during Winter I find that a two day weekend isn't long enough for me to recharge, the first day I spend exhausted, & the second day I spend resigning to the fact that it'll all be over the next day. Yes, I realize this is a terrible mentality. But with a three day weekend I was able to really enjoy the middle day