I also finished Duolingo last year. Levels.7&8 appeared for me in May without any notice. All my previous legendary levels were removed but I am not starting over. Some people who have finished did so again by testing out of each section. I feel there is always opportunity to learn or reinforce my knowledge…doing about one unit per day.
4 months later, I’ve reached score of 106 from a score of 100. At this pace, It will take me 16 more months to get to 130.