Your septic tank acts as a filtering system for the waste going from your house to your drainfield. The solids in your waste stream collect in the tank and the effluent (water) continues on to your drainfield. Over time your septic tank builds up with solids to the point that it can no longer do its job properly. It will either back up or send solids out to the drainfield, which can shorten the life of your system. Having it pumped out on a regular basis can help prevent either one of these scenarios.
It varies for every household, depending on the size of the tank, the number of people in the house, habits etc. A good rule of thumb is every three years.
The baffles on your tank are the part of your tank that keeps the solids in and lets the water out. On older tanks, these were made of concrete and were cast as part of the tank. Over time, gases in the tank corrode some of these baffles and it is a common thing to find these missing on the tank. Repairing a missing baffle is usually an easy and relatively inexpensive repair, using a Polylock extend-and-lock and a PVC T and a short length of PVC pipe.
If it is, simply pumping your tanks is not going to fix it. It is because you have a second tank with a pump in it and for one reason or the other, that pump is not working. Either the pump is no longer working, your float switch is not working, you have a wiring problem, or your pump has become disconnected from the discharge pipe.
We do inspections before real estate transactions to ensure that a septic system is in proper working order.