I think you need to find what suits you as we all have different schedules and internal bodyclocks; you might need to experiment. The important thing is to make the plan 'fit' you and your lifestyle.
If you're hungry between meals, then snack on Superfree for preference, but try to ensure you're not snacking because you're bored or thirsty. If you find you regularly do need to snack, perhaps you could consider making your meals a little bigger? I rarely eat between meals during the day, but that's just the way I am!
I use some of my Syns for additions to meals - ketchup, salad cream, gravy, etc. - and some for a treat item, usually enjoyed with my late night cuppa. It might suit you to have eg some crisps at lunchtime. Just get to know what suits you and good luck.