Yes, there is a life span to aluminum tanks, but the conditions it is subjected to are a big factor in the life span. Usually, aluminum tanks develop corrosion as a result of the boat itself retaining moisture, which eventually comes in contact with the tank.
Also, if water gets into the tank and is present for a fair amount of time, corrosion can develop from inside the tank.
The tough part is determining if there is active corrosion in/around the tank. Most of the tank is not visible or easily inspected. See what you can see of the tank and any surrounding structures/compartments. If you have water present, then the tank may have some issues.
Replacing the tank can be quite a process, having been there done that. . . . and it is a bit pricey, but safety matters.