How long do you all practice your languages for?
Really depends on how much time I have. When I was starting and I had a lot of time I would do 100-200exp per day. Nowadays I often have to skip a day because I have finals approaching and a lot of other things to do, but I plan on getting back on track in the summer.
Anyhow, I personally don't think Duolingo xp is a direct measurement of how much you practice the language, as the website itself is not sufficient. I have a language exchange friend which whom I sometimes communicate. I also like to write down all the words I learn in a Duolingo lesson and then practice them by myself without using Duolingo.
Timewise, on good days I spend an hour or two of total practice.