They shed when they need to, young ones will shed more often as they grow. As a rule of thumb Adults will shed 3 to 6 times a year so the experts tell us...... But....... I find it varies depending on a few factors but I have had them shed a couple of weeks apart. It is a natural thing for them and unless your python is having incomplete sheds, you should not worry. If the shed is incomplete, it will probably be something to do with husbandry issues. It pays to check the shed to make sure the eyes have shed. It could be harmful if the Snake has what is called Retained Spectacle, you need to know what you are doing to remove them, usually it is a Vet visit.