Water softeners are designed to provide years of trouble-free operation, but they do require some maintenance in order to ensure optimal operation.
First and foremost, the brine tank should always have an adequate supply of salt. Check regularly and always use good quality salt designed specifically for softener systems.
It is also a good idea to clean your brine tank every year or two. Let the brine tank use up most of the salt, then scoop out the remaining amount. If a sludge has built up on the bottom of the tank, it will interfere with operation. It can usually be removed quite easily. Use a stiff brush and water to clean any residue from the sides of the tank, remove this dirty water, rinse the tank and reload with salt.
If your system is reaching seven years of age, the resin tank (the tank containing the resin beads) may be nearing the end of its life. Have it professionally inspected. It may require replacement or at least the resin beads may need to be replaced.