I don't think I've seen this question asked, I've seen "Where" but not "When?"
My answer, as often as I can but what works best for me is in the morning, before the day starts. It gives me a good outlook on the day. When I used to work for a living, it was every morning before work, but now that I'm retired, don't really have the time to do it every morning, but do it when I can. I don't prefer evenings because I don't like having to get up during the night and let that tiny bit out that I didn't eliminate the first time.
the hoseman