Not as good as freshly canned, dark colored jams and jellies esp. will change color. I don't know about pickles, but what about freezing the fruit (or juice) and making jam/jelly a month before the fair (to give it time to set)?

I have somewhat the same problem. Our county fair is also at the end of July and nothing is canned yet. It used to be Labor Day weekend which was perfect.

But consider that everybody else is in the same boat, so your canned stuff should be equally "aged" - shall we say - as the competition's.

I think my salsa gets better the longer it sits - just like a fine wine LOL. I just opened a quart of dill pickles from two summers ago (don't ask where I found them) and they're still delicious and crunchy. Honestly I really didn't notice any color change or deterioration vs. last summer's batch.

I agree with ajsmama on freezing fruit to make jams, jelly, etc. which is what I do anyway. Jam making is FUN in January when the house is cold, plus I get more juice from frozen fruit as opposed to fresh.

I've found that the lighter colored jellies may turn darker, but my dark jellies from 8 years ago still look as good as the week after processing.