[QUOTE=Scbb1;2606174]I read the link you attached, it says that you can only use the FMM for one entry but that you can use it within 180 days?[/QUOTE]Technically, the FMM is only good for one entry / exit. If you fly into and out of Mexico they will make you get one when entering, and they will take it before you board the plane for home.
However, Mexicans are nothing if not pragmatic. There is no way to make everybody exiting at San Ysidro surrender their FMMs. And if there were, the lines would be horrendous. The same goes for entry. So, they let you keep your FMM when coming and going across the land border. At least for SY and Otay. I've never crossed with an FMM at any other crossing. Maybe others can comment on Mexicali, or El Paso, or Los Algodones.
