I can find no reference to freezing antibiotics, so I don’t know I would say that refrigerating them should help extend self life.
Whenever I would purchase antibiotics for research laboratory use, I would store them in the freezer at -20C. Antibiotics for research are sold in powder form, and can be stored indefinitely frozen. When I would make antibiotic solutions, I would store them in the freezer, too. The solutions lose potency when thawed and frozen again, so I would store the solutions in quantities that I could use within a few days. Tetracycline solution was made in alcohol, which does not freeze solid, so I never had to thaw it out. Many antibiotics are light-sensitive (especially tetracycline), so it is best to wrap them in foil to protect them from the light.
Oh, one other important point is that laboratory freezers do not have a defrost cycle. Antibiotics stored in a regular home freezer, which self defrosts, will deteriorate. You need a non-defrosting freezer to store medical supplies. When you want to defrost the freezer, you have to make sure to keep the medical supplies frozen in an ice chest or another freezer.