Maintenance and repairs are needed at a mix of mileage and age numbers. The harder the workload that you put on the equipment, the more often it will need tender, loving care. You might not put that many miles on your equipment, but exposure to the elements and degradation over time do enough damage on its own to require regular maintenance.

The manufacturer’s manual should tell you how often it expects you to have the equipment undergo maintenance, but six months is the maximum wait time between checkups for basic trailers with no extra equipment and minimal use.
Just for incidents requiring roadside repairs, recent numbers show that rigs are averaging one every 10,000 miles. If a rig is making 500 miles a day, that’s a month or less between roadside breakdowns. Blown tires account for some of that, but other issues are ones that could be mitigated with more frequent diagnostics and repairs. The cost of the testing and repairs will end up less than multiple roadside breakdowns.