SW used to give you your syns on a weekly basis but changed to to stop the binge/ starve cycle that could happen. However it depends on you really. I personally couldn't save up all my syns and use them over a few days like some can, plus I need the daily treats to keep going. If I saved up the syns for a weekend for eg, I think by the time I wanted to use my syns I'd be feeling deprived and go way over the 105 because of how I was feeling.
But if you are confident that you can save them up and use them as a weekly amount then do so. Whatever works for you as after all this is meant to be a sustainable plan for life. As long as you still loose weight and feel ok with it that's all that matters really.
a SW consultant will not encourage weekly use though. They are more likely to encourage daily syns and a flexi day on top of that xx