I'm not a syn saver but one week I just didn't want or need as many syns. I ended up having about 30 syns over a week instead of 70.
I'd been on plan for about a month at the time and lost 4.5lb that week. It worked out about 1lb more than usual for that time.
My consultant did tell me that a man in one of her other groups tried to save syns but it made him STS.
I haven't actively tried to do it as I am losing continuously at the moment and am aware that I may need to change things if I plateau in future.