Ppl do and you can, for me it doesnt work I save odd ones occasionally but if I had like 90-100 all in one go a few days before wi I'd never get any losses so I have mine bit each day. But try it for you some ppl are fine doing this.
The official sw line on this is that you can as long as you are sure it won't make you feel deprived the rest of the week.
Some people though can't save syns as it affects their weight in (as above) others find its fine. The answer really is to try and see if it works for you. A good idea is to still use a small amount each day so you dont get the deprived feeling.