Yes, K&N filters are bad for rings especially in dusty conditions. The filter need to be serviced properly about once a month depending on conditions. If you ride in a group and ride for a few hours every weekend, the filter should be serviced after each ride. If you use a pre-filter sock, the sock needs to be cleaned after each outing, but the filter may not need servicing for a month or so. If you intend to stay with K&N, it's best to have 2 filters; one in and one ready to go in. Proper servicing takes about a hour or two using the K&N filter service kit. K&N's flow more air, but unfortunately they flow more dust too. Those fine particles of dust can wear out rings in a relatively short time. Extreme example: I bored a cylinder, installed a new piston and rings into a Yamaha 100 for a kid who was racing motocross. He didn't have the money for a new air filter, so he taped about 4 layers of an old nylon stocking over the inlet bell of the carb. He raced two semis and a final the following Sunday. On Monday he was back at the shop and said after he finished the moto, the bike died and he couldn't restart it. It had no compression - I took it apart and it needed bored out again - the rings were paper thin on the intake side - I told him I would not fix it again if he did not put a good filter in it - I fixed it and it wasn't too long after that the crank went bad - it was never fixed after that.
Shop Owner and Mechanic with over 50 years experience