Basically yes they are out growing the skin. yes a snake will shed for a handful of reasons mostly growth but injury such as a small cut or abrasion will often trigger a shed, mite infestation can as well. Burns rots and many other things will cause a shed often if there is any break in the skin the snake may shed. Breeding cycles, ovulation starting triggers a shed as well. In Boas it is documented that the pheromones released during the shed cycle signal males that she is ready to breed. I have never seen any evidence with pythons but it is a reasonable guess. It is a pet idea of mine that the hormonal smell of a shed can cause a cycle to start in other snakes it always seems that when one starts the others often follow in short order I have had 7 of 11 all in shed in the same week. It seems to many to be random.