My husband has been in the States for over 20 years. I've been with him for 10 of those years and unfortunately, his sexy foreign accent gets less and less noticable! Oh well, that's the way it goes
I can hang out with Czechs speaking only Czech after 2 years and a half, and know many foreigners (even Americans) who speak Czech fluenty. It's not easy but definitively possible, here you have a few tips http://blog.lingodb.com/2011/07/how-to- ... ublic.html