when to buy a bigger tank

my bp is almost a year old now. he is in a 20 long tank and is about 33inches long.he is almost outgrown his new hides i just got and i wont be able to fit bigger ones in the 20 gallon.i was thinking about getting him his 40 gallon tank soon but i dont know if it would be too soon.he feeds everyweek with no problem so i dont think it would be a problem but this is my first snake so i would like some opinions thanks

Hmm.. the basic rule is that the tank length should equal half the snake length. But that sometimes gets tossed out the window with tight-space loving BPs.

Also, I would recommend a 30g breeder tank over a 40. 30 breeders are 36x18x12 roughly and are a great adult tank. Most other tanks are too high and narrow for BPs and would only be tougher to maintain heat and humidity in.