I've only had my retainers a week and am still learning what I can and cannot do. I am a 53-year-old who had braces almost 40 years ago but whose teeth had rebounded after having wisdom teeth removed, especially around a broken tooth with a crown - right in front. My original overbite and overjet is mostly back.
I go to a highly-regarded orthodontist in my area. We're doing Invisalign Express with 10 trays, with the understanding that it may not be quite enough, and I may have to have additional ones - with the regular Invisalign fee. However, my dr. thinks he can make any additional necessary correction with a retainer, without having to go that route.
The pain I mention above is from cuts on my lips from the lip spreaders, at first. Now that they've healed, I have none.
It's really too early to rate my satisfaction and determine its worth.