No, its advised that you dont save all your syns every day for one big blow out - although i know many people that do and i myself even cut down some days to compensate for a weekend.
Its for those occasions where you know your not going to be able to stick to 15 syns due to drink, food, party etc that you can set yourself a realistic amount ie 40 syns that you can stick to and stay in control. Its just damage limitation really. So you then count your syns that night until you reach the 40 and then you stop and get back on plan the next day
I am new to sw too so haven't tried this, but it sounds like a really good concept. Basically if you know you are going to go over your syns on the odd occassion, you sit and work out a realistic amount you could stick to. You then make sure you stay inside this. Next day, you carry on as normal with your syns - you don't cut back. Obviously it will affect your weightloss for that week, but it means you stay in control, and shouldn't feel guilty, and you don't punich yourself by cutting away back for the rest of the week. Altho it will affect your result, pschologically I think its really good.
Obviously you wouldn't want to be using this technique a lot though.
Sorry but that's not what flexi syns is about - it not's cutting back on syns one day so you can have more the next or to make up for a binge the night before. Flexi syns is for those once in a blue moon occasions where you plan in advance to have an increased number of syns that day and you stop when you reach that number. It's about remaining in control of what you eat and you get right back on plan the next day without having to cut back.
Flexi syns are totally different from your daily syns and shouldn't really be confused with weekly totals or dialy totals etc. They are used for important occasions such as birthdays, weddings etc not for a blow out at the weekend xx