We usually purchase the ERC-09 ribbons. They come in a purple ink or a black ink.
The printer ribbons have a shelf life, when still in the original blister pack, of 12 months from the manufacture date, regardless of ink color (black or purple), but when you take them out of the blister pack, the black ribbons will last for approx. 3 to 4 months, and the purple ones will last approx. 4 to 5 months. The reason for the difference is that the black is a pigment-based ink and the purple is an oil-based dye. The dye will take a little longer to dry out than the pigment.