I've read here that it's best to apply for N-400 after the Green card's 3rd anniversary because someone got their application denied but I believe the person was not in the USA all this time living with the US Citizen spouse, something like that. It had to do with the residency requirement:
"if such person immediately preceding the date of filing his application for naturalization has resided continuously, after being lawfully admitted for permanent residence, within the United States for at least three years, and during the three years immediately preceding the date of filing his application has been living in marital union with the citizen spouse (except in the case of a person who has been battered or subjected to extreme cruelty by a United States citizen spouse or parent), who has been a United States citizen during all of such period, and has been physically present in the United States for periods totaling at least half of that time and has resided within the State or the district of the Service in the United States in which the applicant filed his application for at least three months." Taken from: https://uscode.house.gov/view.xhtml?req=granuleid%3AUSC-prelim-title8-section1430&num=0&edition=prelim
I do want to apply to N-400 as soon as I'm eligible (90 day window) as I've lived in the USA all of this time with my US Citizen spouse.