Britesea, are these freezer/fridge jams or
canned jams that you are finding have a shorter shelf life?
Back in the 70s my Mom used to can batches of fruit (peaches, pears, apricots, apples, cherries) in just water because she wasn't into all the sugar for herself when she ate canned fruit (she canned the rest in a pretty light syrup for the rest of the family). We had jars of that fruit that lasted just fine for up to 3-4 years in a few cases. My Mom stopped canning certain local fruits when we left the Okanagan in 1979 and I opened a jar of apricots in 1981 after we moved to a new community (the moves and locations are how I know the dates) by accident (didn't notice the "no sugar" note on the lid) and knew immediately when I tasted it that it was one of the just water batches. Colour, texture, taste (if you like bland water canned fruit) was still just fine and my Mom enjoyed the rest of the jar.
I've got several varieties of Pomona's pectin jam, some with very little sweetener (honey and maple syrup primarily) and some with no extra sweetener that are lalbelled 2011, we just opened a jar last week and it's still lovely