It varies from person to person.
I hit a plateau right at 400 and it was stagnant for a long time (I weighed 195). I started training heavier, working on deads and squats. Eventually, I could hit 365 for 6 before I was forced to stop for 2 years (it sux but I had no choice). I gained a lot of mass by doing this (up to 225~230).
You are the in the prime position to make gains due to age and such. Keep training hard and you will crash through 400 before you notice it. If you are anything like me, once you hit 2x bodyweight it will take a toll on your body. I was always sore in my ribs more than muscles. It was a good thing.
To answer your question, it took me about 24 months (age 17-19) to get from 335 to 400.
335 was my plateau for a long time.