When stored properly (original sealed container in a nitrogen filled storage cabinet), spheres will realistically perform well in even the most demanding applications for years. Honestly we are perhaps a bit conservative with our shelf life specification (commonly 1 year from date of manufacture). To ensure that the spheres have been stored adequately here at Indium, we perform functional tests to verify they are as good as when they were first formed. If they pass our inspection after 6 months, we are confident there is (conservatively) one more full year of shelf life from that point.