Anything with high sugar content (or vinegar for that matter) will stay preserved almost indefinitely. It is best to refrigerate jellys, jams and other such preserves though, since, as Booldawg relates, various type of fungus can grow on top of opened jars but won't penetrate the product itself. I revisited my grandfather's old farm house recently ( I live in the U.S.) and the root cellar still had some canned goods in it that have to be well over 50 years old... the jars of strawberry preserves look like they were canned yesterday... There really no other preservatives added... some cooks do add pectin to help set the product, but it adds no preservative value... Best of luck!