One of the things I did earlier today was to go through my box of old seed packets so I would know which ones to order.
Seeds have a finite shelf life when it comes to their viability, which varies according to the type of seed. If you use old seeds, the germination rate can be really low which can be a waste of your time, potting soil and containers. However, there are many types of seeds that last a surprisingly long time. Knowing which is which will save you money.
I just found a fact sheet on vegetable seed viability at the Virginia Cooperative Extension web site. They list the number of years each type of vegetable seed lasts.
Lettuce seeds definitely win the prize for longevity at an amazing 6 years. Seeds that last for 4 to 5 years include cole crops (beets, cabbage, cauliflower, kale and rutabagas), cucurbits (cucumbers, squash and melons), and nightshades like tomatoes and eggplants.
The shorter-lived seeds include parsley, parsnip and onion at just 1 year, and corn, leeks and peppers which have 2 years of viability.
So take a look at the fact sheet above and go through your old seeds to see which ones need to be tossed and which ones are good for a few more years.