I'm having problems with my "words learned" section.
I have about 750 words in the list of words I've learned, and I've noticed that many of them have been accumulating near the bottom, unreviewed in up to a year and at "overdue" status. I attempt to re-gild my tree regularly and I know that I've seen some of these words in my reviews, so I don't know why this may be the case. This issue is also present in the Spanish course, where nearly half of my words are in this state and haven't been reviewed in up to four years. Does anyone know what may be going on here?
I am not sure how that works. I have been working on getting all of my words to full strength. I have found that the best way to do that is by just doing general strengthening. I have been steadily on Duolingo for over 5 years and find that some of my words haven't been touched in 2 years, which like you, I find difficult to believe. I am almost done with getting everything to full strength. Sometimes if there is a group of words from the same lessons, I'll do several strengthening exercises in that lesson. It's been like that since for as far as I can remember.
The same thing happens in the French course. Sometimes I can target certain words by finding out which topic they belong to, going into that topic, looking over the individual lessons until I find the "weak" word, and then redoing that lesson. There are just several words that never show up in the strengthening practices, so you don't ever see them again unless you go back to the lesson where you learned them. For some words, I can never find them again...