drop in air filter
 

I'm planning to get HKS drop in air filter and was wondering if I have to keep replacing it after certain mileages or can keep it forever? Any cons about aftermarket drop in air filter that you guys like to tell? which is better when comparing stock and aftermarket for a long term usage? Thank you.

https://www.hks-power.co.jp/en/support/faq/intake.html

It says to replace every 6000-10,000km which in miles would be 3000-6000mi. Honestly just get a K&N filter and as long as you dont over oil the filter you should not have any issues. There really arent any cons about aftermarket air filters just make sure you keep them clean.