After wearing about 19 out 31 of my Invisalign trays I needed a new set of aligners. This one contains 52 trays.

I agree with Jay. There is no way to tell without photos model or xrays what things look like.  . It's
pretty unusual for a mild-moderate case of crowding to require over 2
years of treatment.  Have you been compliant, are you wearing your trays 22 hours a day.  All these things matter

Remember, when doing invisalign, you are not buying trays but buying doctors knowledge and expertise. Invisalign is as good as your doctors experience. When some cases take long, many cases should not take more than 12 to 18 and maximum 24 months. Make sure you find a good experienced orthodontist specializing in invisalign for a second opinion.

You mentioned that your teeth were not that crooked to begin with. It's pretty unusual for a mild-moderate case of crowding to require over 2 years of treatment. Most of my cases are complete in less than 1 year. Please be aware that without photos, models and x-rays of your teeth there is no way I can tell the severity of your case. Also, there is no way I know how compliant you were with wearing your aligners.