Certified GKH Gardening Expert
It is hard to put a definite date on it due to the fact that there is many factors that will determine how long seeds will stay viable. At te very least, the seeds should be viable for at least 2-3 years. If stored properly, it may even be longer that they will remain viable. There is no harm in trying to germinate old seeds. Plants that come from old seeds are just as healthy as plants that come from fresh seeds.