As long as he/she wants! However you may create an obstacle to becoming a citizen if you are gone more than 6 months per year. If you have not received a "green card" you will have to obtain "Advance...
You need to be a permanent resident card (green card) holder to be eligible to apply for citizenship.In normal circumstances, an immigrant should be a permanent resident for five years to be eligible...
Marrying a U.S. citizen DOES NOT confer automatic citizenship or permanent resident status to the non-citizen spouse. The non-citizen spouse will have to apply following the standard immigration...