I personally only use the bags that sys "freezer bags" to store food in the refrigerator or freezer. I feel the "sandwich bags" are too thin to properly store food for a long period of time. For storing food I go by what is recommended for the particular food product.
It depends on what type of food, but they aren't vacuum sealed bags. For foods that you would refrigerate I would only keep them up to a week. Other than that, things like crackers, I would check the expiration date.