Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Turface is available at several places in the San Francisco Bay Area.
Fine substrates with a high CEC can 'expire' if you are skimping on the fertilizer. Then the fertilizer is used right away by the plants, and they draw on the reserve in the substrate. If you follow a more generous fertilizer program then there is some give and take but the substrate remains rich in fertilizer.
So, in the sense that the substrate runs out of fertilizer, yes, it can 'expire' if you treat it wrong.
The particles can break down. Aquasoils seem to break down relatively fast (few years). I have been using Soil Master Select (about the same as Turface) for several years now and there is no sign of the particles breaking down. Sands and gravels do not break down in the life of the aquarium, but they are not very good for growing plants. I have seen some tanks with Flourite that had been reused for at least 1 change in aquascape, and it (the Flourite) seemed intact. I do not know how old it was when the rescape was done, nor how long it lasted.