I get what you're saying Mac, but they are a good (and easy) addition - I and many others have had no problems with them. With the Norton spin on set up, you can use relatively cheap Citroen 2CV filters. Part of the reason for my wrecked engine was the disintegration of four fibre ATD gears (don't ask), the debris from those shredded gears caused havoc in my motor, especially with a plain timing side bush. Don't tend to run the oil much beyond 1200m, even with a filter.