The family next door to me moved here from New Jersey when the husband and wife graduated college, so at least 20 years ago. The east coast accent is gone but speech patterns are still east coast ie; harder sounding consonants and vowels. I learned French here in the U.S. and when in France, no one there can hear a regional accent, which in many countries can identify the speaker's birthplace. Other folks I know have never lost their accent, although in many cases the accent has softened.