I'll echo the same thing: all snakes grow their whole lives, but they slow way down, the older they get. They grow, so they shed...& those sheds get further & further
apart. I've had snakes that only shed about every year to year & a half, so obviously they didn't add much length.
The BCI I had, I took in as a yearling, & it seemed to take "forever" for her to reach 6'. Actually it was about 7 years, and by the time she was 12-13 years old she was
7 1/2' long. She was about 8' when she passed at age 18. (she lived her last 5 years with friends of mine that were into bigger snakes)