I have been cycling for almost 4 months and on the same 20 mile loop with some hills I went from 15mph on my first month, then 16 mph on my second month, 17 mph on my third and now I have hit the 18 mph mark. I only train a little but I am worried that I might hit a plateau and stop making gains. If I keep this up for a few years will it be possible to at least reach at least 22 mph?