They grow very fast. My 7 month old is already about 35" long. Common saying around here is that "they grow like weeds...."

Don't be afraid to bump up prey size if you see them having a very easy time with the size you presently feed them. They do appreciate good sized meals, and their growth will reflect that. Its also good because you can feed at longer intervals. Captive snakes have been know to do well on appropriate prey items less often than smaller prey items more often.