I've got some 0.3 Green Devil bio that are over 5 years old and had a few issues with some not feeding well in a 6.01 inner barrel. But, having checked the majority of them with a micrometer most of them were still solid and showing a regular 5.96mm diameter, even after all that time. If you keep them in a container and mostly in the dark then they should stay fine until they get used and then left to rot down in soil, which is where the bio-degrading is supposed to start. Rather than chuck them, check them for size first.