Yes, once you get them taking big foods they grow really fast, mine is around 2 yrs old as far as we know and 24 inches and very thick, he has really started to motor now he is in my tank as he now has lots of room, lots of whole foods and lots of clean water in low Nitrate.
You should see 12" to 15" in a year easy.
You can literally watch them grow if you feed daily on shrimp, earthworms, mussel, whole fish like smelt, add vitamins to my frozen food (aquatic spray on vitamins) as I worry about thiaminise in the prawns/ shrimp / crustaceans etc. Mine will now take the larges lob worms which are over 6 inches long, he can do 10 and still be looking for more food. I also use Krill but that seems a little messy. I also try to sneak in a mix of sinking pellets but he is pretty good at avoiding those so far.
I also use frozen but cooked prawns as I THINK the cooking helps remove the Thiamin, I also thoroughly wash the frozen king prawns as some have Sulphites added to help remove bacteria.