As a newish rider myself (3years) I took my test on a 125 bought a 500 and rode it "restricted" for 18months re-took test (I know it expired in another 6months but couldn't wait). Bought my ST2 and not looked back. Can't imagine ever getting to the point where I have "outgrown" this bike, although I reserve the right to change my mind (and ride something else).
However the best thing I have done is continued my training and will continue to learn, no one's perfect.
I love my bike so much I've started learning how to take care of it - cleaning and basic servicing. Getting good at passing spanners to those who know how to use them.
SA
p.s. goodluck with your test - be sure to let us know.