Depends on the storage conditions and the type container.

Sunlight degrades nitro. Cans don't allow sunlight in. Clear or milky plastic jugs often do.

Heat causes evaporation. Storage in temperature controlled conditions controls that.

When I got back into the hobby awhile back, I pulled out a case of fuel and used 3 of the 4 gallons. That fuel worked perfectly. It was considered to be VERY old by some of the guys. It'd been stored in the closed cardboard box in the house. Why only 3 of 4? One had been partly used. The cap no longer had the plug seal and the contents were "evaporatively condensed" and little remained.

If your jugs are still full, and no sunlight's gotten to it, the fuel should be good.