I can't give you exact numbers, but the life of the stuff is legendary. There are tales of newspaper photo editors keeping the stuff in their desk drawers for years and just throwing whatever came in together in the soup––long after it had turned brown and nasty. I have used it when it was dark brown and chunky–no problem. I just screened out the solids and kept using it. That batch finally got thrown out by someone else who had no idea what it was (so much for good labeling) but I never saw much difference in the way it worked.
There is no replenishment system. Use it until it doesn't work and then dispose of it.