The rules are pretty clear for citizenship through naturalization, and if the the OP cannot meet the 'continuous residence' requirement, he is therefore not eligible:
Eligibility Requirements
If you are a green card holder of at least 5 years, you must meet the following requirements in order to apply for naturalization:
Be 18 or older
Be a green card holder for at least 5 years immediately preceding the date of filing the Form N-400, Application for Naturalization
Have lived within the state, or USCIS district with jurisdiction over the applicant’s place of residence, for at least 3 months prior to the date of filing the application
Have continuous residence in the United States as a green card holder for at least 5 years immediately preceding the date of the filing the application
Be physically present in the United States for at least 30 months out of the 5 years immediately preceding the date of filing the application
Reside continuously within the United States from the date of application for naturalization up to the time of naturalization
Be able to read, write, and speak English and have knowledge and an understanding of U.S. history and government (civics).
Be a person of good moral character, attached to the principles of the Constitution of the United States, and well disposed to the good order and happiness of the United States during all relevant periods under the law.
Whether they pull the green card upon entry is a different matter; you've been lucky with that up to now.
