I have had my braces off for a year and a half. I was missing one tooth from the second tooth on the left top with no space for it. My teeth were in excellent health but extremely crowded and crooked. My ortho was effing phenomenal.
We removed one tooth from the bottom center and set out to open space for one in the top. The reasoning was the eye is drawn to symmetry at the top where they are visible while smiling but the bottom it is more important to just be straight. I wore my braces for just under two years with expectation of an implant going into the space on top. When the day came it made more sense to go with a bridge there because of the space and symmetry. I've worn my retainers at night pretty much every night since then and have been extremely happy with the results.
Important note: I went with the Damon brace system (self ligating) and had not one moment of regret. Fewer adjustments, no broken brackets, only one broken wire (damn ice). I swear by them and strongly urge anyone considering braces to visit an ortho who specializes in the Damon system. Yes, I believe it that strongly.
Damon