Find out if your local county or municipality has a required timeframe. By us it’s every 3 years.

As far as how to tell in the short term, is there a tank between your house and the drain field that you can access (has maybe a round metal or concrete cover or a plastic riser with lid)? If so, lift the lid and see if you can see the top of the pipe going in the direction of the drain field. If so it’s likely draining fine. If the liquid is near the top of the tank and you can’t see a pipe, you’ll want to get someone to look at it sooner rather than later.