That all depends on how hard you drive your car, the condition of the engine and oil already, the environment your driving in, the efectiveness of your air filter, etc. I guess it comes down to what you believe the quality of the filter is like. Same goes for spark plugs, if your happy with $5 plugs on an engine that you have invested a lot of money into then thats your choice. I have used ryco filters on my old bombadore and found them OK, although you really need to compare them to something. So maybe note the engine oil colour and smell and then change to a different filter at the same interval and see if you notice a difference.