Cats tend to reach close to their adult size by 1 year old, but may continue to grow slightly until they are 2 years old. (This of course refers to overall growth, not horizontal growth due to too many kitty treats!) This generally hold true for all breeds of cats.
Bengals usually take 2-3 years to reach their full growth. I think they reach full coloration by the age of 1 year though. Growth can vary a lot by breed. Ragdolls for instance take about 4 years to reach full adult size and coloration.