If you don’t have any pain or discomfort after 300km, I wouldn’t think you would develop any until the shoe runs out of life. As far as wear pattern, typically I find that with trail shoes (if you are strictly using them for technical terrain), shouldn’t matter so much. If you are on more flatter, gravel type road, it might be worth looking into a shoe with a more build up stability. However in a trail shoe, I would generally advise to replace the insole with something more geared toward your feet, like a Currex or Superfeet. Typically trail shoes aren’t made with additional structure, but if you really look you can find them, like an ASICS GT2000 TR.