Hello friend,
You must try to check it up for every 30 to 45 days, but if you are too busy and not getting time to check then contact to any professional and learn basic tips of checking,so that you can help yourself by your own and don't have to invest more money even.As you told that your house is too old and you have lot of trees also so it's important to take measures before you will face any problem.
Regards,
Nelson
Sewer And Drain Cleaning 