Theres been a few threads on this and it can get quite 'interesting' the differences of opinion. Have tried to search for the more recent ones but can't find them grrrr!
Its something I 've never particularly done myself and I have started weighing in on a Monday morning at home I think its a good job I don't as think I could get through one hell of a lot of syns after weigh in! Personally I am trying to develop as 'normal' a relationship with food as possible and eating things just because I have stepped off scales isn't the norm I feel but I do allow myself my treats within syns through the week and off plan days/events as they come up.
If arranging meals or eves out I would tend to do it earlier in the week weigh in wise when I was attending group but now am weighing at home I can take that into account for myself and not have to explain to anyone anyway so that suits me.
Some people can 'get away' with it but that could depend on so much, what their interpretation of a blow out is, how much else they have consumed that day/that week (some don't eat till after wi so may not consume many more syns/cals than on other days overall)
There are theories though not sw that zigzagging your bodies intake can work for weightloss so it might work in some peoples favours!?
I think we are all different and need to do different things to 'cope' and keep going with dieting and if it works then fine x