My snakes haven't gone into shed in months???

[Neal]

Every snake grows and sheds at their own pace, so it's probably normal. 4-6 weeks is an average for young BPs, but there are also plenty who fall outside of that range. My juvenile BP sheds every 2 months. Just make sure you are feeding them the correct sized prey (10-15% of their weight, prey as wide as the widest part of the snakes body). Once a snake has reached full size it will also shed less, I have heard of some adults only shedding a few times a year.

Also:

It varies on how often you feed them, the size and also the species of snakes. More so because some grow faster than others because their metabolism is higher. If you're snakes are healthy, eating and defecating regularly then I wouldn't worry.