Track very occasionally, wheels even less. I don’t seem to get much dirt. Certain areas seem worse than others but usually it will be a section about an inch long. Why are you getting dirty track and wheels? Do you clean the rolling stock wheels. If any of it has plastic wheels they seem to attract and distribute dirt at a fast pace. Have you over lubricated your locos?
You need a better title for your post, it doesn’t actually attract attention. Why not 'How often do you clean your track' for instance.