How long can a US citizen stay abroad?
AnswerAs long as they so choose. US citizens do not lose their citizenship simply by traveling for extended periods of time outside of the US or even if they establish residency in another country.
As a US citizen you can stay outside US as long as you want to after becoming a US citizen. Unless and until you commit any serious crimes which would affect US safety your citizenship will not be revoked. While you stay outside US you should file tax returns and abide with the law as a US citizen and also follow the rules of country you have moved to and intend to stay in.