Many of us have learned (or at least tried to learn) a foreign language. Depending on the course, we spend about five hours a week in class, and then maybe another five hours worth of assignments and studying. For polyglots, they put in that ten or more hours of work every day, depending on the person. Most of the polyglots that I was able to read about have pretty strict study routines that are based around maintaining the vocabulary, grammar, and written forms of the languages they are studying. Some of them also listen to audiobooks in foreign languages, travel to immerse themselves in the language and culture, and have conversations with native speakers that they have met in their travels, all in an effort to keep up with their language skills.
This blog is not to say that anyone who puts in ten hours of work a day into seven different languages can learn them, because that is simply not true. Some research has shown that there is a difference in the organization of the Broca's Area between polyglot men, and monolingual men. Others have compared language to music. Just like some people are incredibly gifted musically, polyglots have the unique ability to quickly pick up on all things language related, but only after they have put in the hours of studying required to keep their talent. I think once you watch the video, you will have a better understanding of just how much work these polyglots put into maintaining their language skills. It's pretty amazing.