What Happens If I Stay In Mexico More Than 6 Months
Re: Overstaying Penalties in Mexico & Staying Beyond 180 Days 7 years ago Personal opinion is that if you deliberately overstay you COULD be stopped from re-entering the country ever again. (That is certainly what happens in the U.S.) Officially there is a fine for each day you overstay but no official process in Mexico is consistent. As for the rest of what I am saying. If the OP has an early flight and the immigration office is closed they will not be able to pay the fine and will miss their flight. I don't know if its open 24/7 in Benito Juarez.
Better to do it the day before and not when you are at. If you continually overstay your visa, then you could have issues when trying to return to Mexico. They may deport you (especially considering which country you are from), and you may not be allowed back in the country for years. It’s better to have a clean record when you leave the country so that you have better chances to get back in next time.