Daily. I am familar with the pattern of my fluctuations. I can usually tell if I will be up before I even get on the scale. I know if my face is puffy or my tummy is bloaty or my muscles are sore. There are rarely bad surprises once you learn your body. I have even had a day where I was really bloaty and puffy and was all excited because while I was "up" I wasnt as up as my up was last week so my up is now lower.
When I realize that I HAVENT seen a number in a long time that is pretty fun, almost more exciting than the new lows.
Plus, one of my first symptoms of going off plan is to stop weighing. It usually stops even before food recording stops.