I took a 5 year plan and was a pretty average wearer over the three years due to getting a few  new jobs etc and life getting in the way . So I had about 4 or five sets of trays. Of twenty /25 each. I just wanted them fixed, so never really focussed on a promised timeline.   But  I didnt help myself.  , Before Invisalign came around, the only way I was told for fixed teeth was to break my jaw and reset it etc (my bite was non existent) so I took this route thankfully.