Duolingo goals: German, French, Spanish
So My original goal for my three languages was to do 20xp a day for each language but Im actually on average doing 100xp a day for each language. At this rate, how long should it take for me to finish the German, Spanish and French duo lingo courses?
XP's are related to the time you spend, not with how well you master the language. You can keep strengthening the first lesson until you have 3400xp, or you can finish the tree without gathering so many xp's. If your goal is to finish the trees, don't strengthen and don't repeat. If your goal is to learn a language, then you strengthen and repeat, take twice as long to finish the tree, but at least you'll have learned something.
In Duo's first year it took less than 3 months to finish French at level 14 (IIRC) doing at least 100 XPs per day. My guess is that it would be about the same now. Anything since then I haven't paid attention to, as my practice involved more than one language each day.
It seems to me now, however, that it is better to finish a course w/ a higher level than the average (which is 12-14, I think), so it would take longer to finish or would need more XPs per day.