I have a Hayward DE-3620 filter (came with the house 4 years ago) which I have never cleaned as it is my understanding that they don't make the D-ring necessary to seal it properly. I backwash as thorough as I can when I close the pool and I don't have any issues with it. I'm going to replace my heater next year, should I also replace the filter? If so, what model? I am happy with a DE filter, so I would prefer to stay with DE.