It totally depends on the individual snake. Some females can get big quickly and end up to be monsters.
Then some can never grow quickly and end up not getting big at all. Nature and genetics play a part in it.
My female is 1 year 9 months and pushing 1500 at the moment, but by no means have I ever power fed her and I never intend to.
Sure, powerfeeding would help it grow 'faster' but that's not good for the snake and if your snake just doesn't have the 'fast growing gene' nothing can change that.