In order to keep on top of your flight experience and piloting knowledge then you should keep up your hours. Generally speaking, to stay current a private pilot should aim to fly for at least 4-8 hours a month. If you do not achieve this then your piloting skills can begin to suffer.
If you have a pilot license and use it to fly privately then you should aim to complete a flight that lasts between 1-3 hours at least once every two weeks. This will allow you to build up your flight hours, and it will also ensure that you brush up on your skills regularly, and that you do not forget any of the important things you need to know when it comes to flying.
As well as flying regularly to stay current, you should also undergo a physical exam regularly to stay current. This physical exam will allow you to get a third-class medical certificate which you need in order to be able to pilot a plane. So it is important that you keep up your flight hours and complete these physical exams in order to stay current.