It greatly varies with the type of seed. I have corn seeds that must be 10 years old, & I still get pretty good germanation (bought a huge bag of them on clearance). I collected a whole sunflower head & forgot about it in my unheated garage for about 4 years, & those things still germanated at 100%. I have saved squash seed & cucumber seed the same way, germanation went way down after the 3rd year so I tossed them. Some seeds don't last long if you don't plant quickly, it's just their nature. On the whole, if your mason jars are stored in a consistently cool, dark spot, they should be good at least 3 years from my personal experience.

I wouldn't freeze them. Fridge might be better if that is what you are looking at.

I agree with Loretta. Some seeds must not be frozen. I store mine in the frig. Some keep better than others. I've found that scallion seeds are good fresh only.

I see we have 2 threads going on this and thought it might be a good question for the FAQs here. Guess what...It's been asked and answered in the FAQ...so here is some more good input...

Here is a link that might be useful: Suggestions for storing seeds FAQ