honestly, i dont think that you will be bored of it! & even if you do get bored of it selling Ninjas is easy because everyone wants one.
With the ninja you'll be able to get the feel for riding and you'll be able to learn your limits and your comfort zone and you can really sharpen up your skills. My bf was one of those people that got bored of the Ninja after 6 weeks, but that is because in his situation he's had experience on dirt bikes, snow mobiles ect.. plus 2 upping on the ninja was less than ideal lol
I think that you'll love it & again, if you dont love it, you'll be able to sell it no problem on Kijiji! My ninja ended up having 8 owners when i sold it and im sure its going to have many more. Its a learner bike, but alot of people just love it, dont need anything bigger and stick with it just because