> Just curious is this 8 year streak for 1 language?

No. Probably five years for one and then switching between others (German, Italian, and Spanish).

> What % completion are you for a the language?

I got close to the end initially then they added more to the tree so I never finished the tree as I didn't need to. I just looked at it and I'm at 50% so they've added a lot since I last checked.

> Do you consider yourself proficient?

I've lived in the French speaking part of Switzerland for nine years. That has made me proficient. Having French speaking colleagues, going to evening classes, giving talks in French, receiving correspondance and filling in my tax returns in French, working in a local gallery (adds vocab and situations outside the norm), watching French films and TV, listening to French podcasts and radio.

Duolingo helped with building some vocab and grammar.

Becoming more proficient in French and living in a French speaking country has, on the flip side, started to erode my English (spelling for the most part).

Anecdata, but I completed the whole french duolingo tree and kept my whole tree "gold" the whole time, and I still don't feel like I'm proficient in french at all. I thing duolingo can be a good addition to another language learning system, but on its own I think it's next to useless

I'm the same with French. A few years later I recall nothing. I am proficient with Japanese which I learned using traditional methods and lots of reading over a few years. There's no magical easy way to learn a language!