Wow, I've found that weighing myself twice a week has been super effective for me this year, but even then I would be disappointed sometimes with the scale results.
Since reading these posts I've become motivated to weigh up every day. Especially while I am in a maintenance phase for two weeks and want to be careful that I maintain my weight and not gain.
I can't believe that there is a variance of about 1kg in weighing! Yesterday I was 80.5 and today I am 79.5. If gaining or losing one kg represents a 7700 surplus/deficit in calories, then it becomes clear that it wasn't extra/less calories that could have affected the scale that way. And daily measuring has taught me that you have to be really objective when weighing up and look at the general pattern.
So many times this year I have been disappointed with my results when I thought I should have lost more or when I gained slightly. When, if I had measured the next day I probably would have found that I had dropped to the weight that I had planned. Awesome to have this knowledge!