Well it sounds like you're doing the right things. I filter through a bag filter into a drum which I have a heating element in. I heat the oil for about an hour twice a day for three days. The heater is on a timer. Then I pump this oil through two Goldenrod filter on it's way to the storage drum.

If you are plugging filters in a few weeks and say less then 4-5K miles you may just have real fatty oil.

What type of on board fuel filter are you using? Is it heated?

A cold filter will plug much faster then a warmed filter. Warmed oil hitting a cold filter will also cool the oil and cause blockage as the fats plug up the filter.

Lastly check you oil is it hydrogenated