Is it really necessary for me to have braces for 2 years?

My teeth are already straight because I had to have braces like 8 years ago. Now they said they just need to widen out the top teeth and fix this huge gap on the left side of my mouth. Well it's been 8 months and the huge gap is basically gone. So now all my teeth touch where as before the whole left side didn't touch. I mean my teeth look like they should now. Why do I need them for another 16 months if there really isn't anything to change.