Simply depends on your ability to practice correctly (deliberately!) as opposed to mindlessly (which is what most people do! :))
When learning on your own stops getting you anywhere, it is a good time to start looking for help (mentors/coaches/strong players at your local club etc.)
To your other question : jumping to higher rating classes takes increasingly logarithmic levels of effort and for most people, the rating climb typically slows down the higher you go, even though it crawls up if you are putting in the work.
So I have been a member of chess.com for about a year now and I feel like I have been making steady progress. Just curious as to what other people's rate of progress was. How long did it take people to get to say the 1700-1800 range? Is there a normal rate of progress for most people, or does it just simpy depend on the individual?