I tend to use around 13 a day, that way if I forget to write something down, I have some spare, and if on the odd occasion I go over, I've got some to recoup back (does that make sense?)
I rarely use my syns because I don't feel I need anymore - I do all green days and it fills me up and I also have trouble fitting in my HEXb's - I love the Alpen bars but find 2 are too much. I do use them on a Thursday because I often have an Indian takeaway because that's the last day of my working week and it's a way of celebrating!!