|The short answer to this question is yes. Old seed can remain viable for quite some time, as in a number of which years. This year I seeded a number of veg and flowers which I labelled as new and old seed, and on the left is Tomato Alicante which has germinated just fine as have a packet of Amaranthus caudatus (love lies bleeding - an exotic looking annual see below)
The success of sowing old seed depends on:
Seed is expensive and if you are growing a small but diverse number of vegetables and flowers there is often too many seeds to use in one season, unless by F1 hybrids when there seem to be a pitiful few in the packet. Once seed was a cheap option but now it's easy to spend £30-40 on seeds so the longer the seed can be kept, the more money saved.
Very often old seed will germinate fine and I would recommend you try it out.
Love lies bleeding on the left is an annual, easy to grow and great in hanging baskets. It prefers sun and in common with many other exotic annuals such as Ipomoea (Morning glory) a cool summer will not suit it, but then it will not suit the gardeners either.