Here's some tips from Sandia Seed company:
How long pepper seeds remain viable depends on how they are stored, but we say that 2-5 years is realistic. It really depends on if they were fully dried before storing.
To store for long term, you need to keep the seeds cool and dry. If seeds are too wet, they can rot in the fridge, or they can get frost damage in the freezer.
If you store seeds in the refrigerator or freezer, place the packets in a small, air-tight container with a tight fitting lid, and ensure the seeds are properly dried to begin with (for best storage, seeds must be prevented from being exposed to any humidity, moisture or temperature swings prior to storing). We like to use mason jars with the plastic lids for storing. You could throw in a packet of silica gel to help reduce any moisture in the seeds – or you could also use a satchel of rice or charcoal to help pull moisture away from the seeds in the tightly sealed container. Then store in your fridge.
When ready to plant pepper seeds, allow the seeds to come to room temperature BEFORE you open the canister/container. If you open the container before they come to room temperature, moisture will be pulled from the warmer air into the seeds, which will make them no longer fit for storage, so you'll need to plant them.
Seed Germination Rates Decrease Each Year:
Each year the germination rates of seeds decreases, so less seeds will germinate than if they were fresh after storing. To offset this, we recommend planting more seeds to accommodate for the natural loss of viability of the seeds over time.