The key to success when freezing seeds is to store the dried seeds in an airtight container and maintain constant cold temperatures. The seeds should be completely dried before freezing, as the freezing process can cause wet seeds to crack or split. As long as they're dry, there's no problem. Many of us store seeds in the freezer to increase their shelf life.
Seeds that have been frozen are likely to grow. It depends on the amount of time they were frozen, how they were stored and what type of seed it is. Seed banks keep seeds in vaults in the event of a global catastrophe and preserve genetic diversity. If it's good enough for a seed bank, it should be good for gardeners, but they forget one important step: drying the seed.
Your seeds are more likely to require stratification than annual seeds, and some will not germinate until two or more winters have passed. It is not true that if seeds are frozen they will no longer be viable: seed banks around the world freeze seeds for long-term storage. If you just want to keep your extra seeds for planting next year, you can try storing them in plastic bags or in a kitchen cupboard or drawer. Yes, it works for some seeds as long as it dries properly, but it's not recommended for most gardeners.
The take-home message here is that there is no “better method of storing seeds” as suggested by most gardening sources. However, seed banks also have specialized equipment for freezing seeds that the average homeowner doesn't have. Pepper seeds (Capsicum annuum) had the highest germination rate when the seeds were left in the harvested fruit for another 14 days after harvest. They may keep rare seeds in storage for many years and need to ensure that the seeds remain safe and viable.
Storing seeds for the long term is a smart strategy if you grow traditional plants or even if you just bought more seeds than you could use. The main advantage for the home gardener who wants to store seeds in the freezer is that the freezer opens much less frequently than the refrigerator. Dried seeds can be placed in individual envelopes labeled with the name of the plant and the year the seed was collected. Many orthodox seeds continue their ripening process after the seed turns black and is released from the parent plant.
Long-term seed storage can be done in a number of ways, depending on how long you want to store your seeds. Stored in an airtight container with a desiccant and placed in a refrigerator or freezer, pepper seeds can remain viable for up to 25 years, but seed vigor plummets after two to five years when stored at room temperature.