Recommended intervals of pumping for optimal functionality range from 3 to 4 years, and 5 at most. Tanks can sometimes suffer structural damage and deteriorate over time.
However, problems occur most often in the plumbing, such as clogged lines or seeping portion of the tank. If your plumbing suddenly backs up under normal use in dry weather, temporary blockage is the first probable cause.
Some pipe blockages are caused by tree roots entering the drainpipes, which can develop over a period of time. It's best to start with a complete diagnosis.