I've already spent about 6 months on my main project, and it's not even close to being finished. Parallaxing, and making your own soundtrack, pluss everything else will do that to the time you spend developing if you can't do it full time, and plan on making a game that lasts more than one or two hours.
Currently, the intro portion alone is looking to be around 1+ hour long, so my main project will probably have 20 hours+ of main storyline gameplay, and will probably take me between 1 or 2 years to finish, going by my current rate of progress.
I think things will speed along once all the basic characters, music, and maps are done. However, there is always the chance of a problem arising down the road, so certainly no less than a year til I finish.