Most kids may take 5 to 10 years to reach 2000, if they persist. The key here is persisting. Most actually quit chess or slow down to put in any effort in chess after they reach middle school. 95% will shift from chess to college application when they reach high school.
For adults, the time may take even longer, due to several reasons: more distractions, less time to play and study chess, and slower in learning new knowledge.