Congrats! Now that your husband has his green card, I would recommend applying for Citizenship as soon as he's eligible.
Looks like he meets the 3-year exception:
Exception for People Married to a U.S. Citizen. If you are a permanent or conditional resident married to – and living with- a U.S. citizen for the past 3 years, you may apply for your United States citizenship at the end of those 3 years. Even if you do not have a marriage-based green card, this rule may apply to you. For instance, if you came to the U.S. with an employment-based green card and married a U.S. citizen shortly after arriving, you may apply 3 years from the date of your marriage. You must, however, provide proof of the marriage and you must stay married to your spouse throughout your entire interview process- you cannot divorce, separate, or even move out without losing this exception.