Of course, learning a language when you are very young makes it easier to maintain that language. We are seeing one thing, in particular, with respect to exogamous unions; in other words, couples where the two spouses do not share the same mother tongue. The number of exogamous couples is growing. Children of exogamous couples are much likelier to maintain their bilingualism because the francophone parent chooses to send the child to a minority school or places them in an immersion program.
The biggest obstacle is this: even if you have learned a language, not having contact with groups who speak that language or opportunities to speak that language lessens the ability to maintain that language. As Mr. Jedwab said, we have seen, in most of our studies, that when contact is frequent, language maintenance is much higher. Children who attended immersion programs are much more likely to be bilingual than other Canadians who had a standard French-as-a-second-language education, even six or seven years after leaving the immersion program.