I have to WI twice a week too or forget it. When I tried going once a week, I would, on occasion, reward a good WI with a candy bar later that day because I had a week to make up for it. Great logic, huh?

Twice a week keeps me accountable.
I did my best when I'd weigh in three times a week, but that was during my "single life." "Married and baby life" only affords me twice a week, but I make it a priority.