Save them, definitely. BUT....do a germination test before you risk your garden's performance on old seeds.
I used up a bunch this year, and tested a whole lot more. The ones I tested almost all were between 3 and 6 years old, and almost all were still in the satisfactory (above 80% strong germination) range. There were two or three complete failures... and all the seeds were stored under the exact same conditions.
I've also had total failures from freshly purchased seeds. My best germination comes from open pollinated seeds that I've saved from my own plants, especially tomatoes and peppers. I suspect that is because they have been kept at consistent temperatures for their entire "life". Not shipped, etc.
To germ test, count out a number of seeds (10, 50, 100 depending on their size and how many you have) and spread them on damp paper towels. Layer two or three towels together so they'll hold up. Place another paper towel on top, and mist it with a spray bottle of water. *Carefully* roll the whole thing up and put it in a plastic bag- but leave it OPEN! LABEL it for variety, "lot number" (maybe the company it came from, if you know, or the year you grew them, or whatever will tell you what package they came from) and set them someplace warm. Well, except for lettuce and spinach which prefer much cooler temps to sprout- those can stay at "room temperature" unless your house is very hot, then you might want to put them in a cool cellar, or test them when the weather is cooler.
I usually put mine on top of the fridge. Start checking them in 5 days, carefully unrolling and peeking- you often don't have to remove the top paper towel at all, you can see the sprouts developing through it. Most seeds will have sprouted all they are going to in an absolute maximum of 2 weeks, especially if you kept them moist and warm.
Open it up completely, and count your results. You need to differentiate between a good sprouted seed and one which just started to put out a root or sprout and died- old seeds sometimes will sprout weakly. They won't do well under garden conditions.
Divide the number sprouted by the number you started with, and you've got your germination percentage.
Over 80% is fine. 70% is acceptable, but you might want to plant them a bit thick. Lower than 50% and you're risking spending a lot of time and maybe money (if you're starting them inside in pots under lights) for nothing. You can try planting them REALLY thick in the garden, knowing that you may end up replanting. In our short season area, we can't afford to do that.
And NEVER plant all your seeds (of any type or variety) unless you are absolutely certain that you can get more. In a SHTF scenario, if you only have 40 seeds, you plant NO MORE than 20. If you get a crop, great! Save as many seeds from it that you'll need for at least two years growing. If it fails- for any of many reasons, from weather to bugs to disease- you've still got a small seedstock to start over from.
Summerthyme