to kill or not to kill gremlins

A few of my friends tried to drop some gremlins in my town, but it says that the town was too full of gremlins, so if you don't smash them and your town is at the max no one else will be able to leave you a gremlin, and then neither you nor your friend will be collecting any goo until you smash them. With that being said, the longer you keep them in your town the more goo they collect.....so that is a dilemma!!