Does Spark-Plug Replacement is part of the Regular Maintenance?

how often/mileage do we need to replace both spark plug inside the Rex Engine, although don't use the Rex much like every 2 weeks or so for few miles just to keep the engine running, so is there any specific miles or time after that we need a spark plug replacement or need to wait until dash will give warning sign or some error will pop-up in ECU for Bad Spark Plug, thank in advanced.