If it's any measure, mine are late 06s, and about the same size as my 2 year old male corn. LOL, that was probably no help at all, but yes, I'd say they are slow growers.

Also, I agree, humidity is very important for this species, along with cooler temps, making them not ideal as a beginner snake because they are not easily forgiving of mistakes.

I would stick with a tub, right now both of mine are in 28 qts.