Jams And Chutneys Preserving/pickling/chutneys/j… Best Before Dates.?

Preserving/pickling/chutneys/j… best before dates.? - jams and chutneys

I wonder how long you keep a jar of jam, if you have a lot of sauce or jam, etc. .. Most of the books explain how to do this or that, but not really a period where you go when it opened?

Ideas please?

Thanks

Funky