Engine mount

I have just been advised that my enigine mount is broken...lucky me. Is this a critical piece that needs to be r/r ASAP? Apparently I have been driving like that for quite awhile so I can't tell if I'm playing with fire or not...anybody had this problem before? I was going to replace the engine anyway but I have to wonder is the engine mount attached to each engine itself or is it added to the vehicle before they drop the engine in?