- It depends, check every 6 month to a year and see how it goes, I'd replace every 2 years at most, but your driving area can make a big difference.
Easy, Private: www.youtube.com/watch?v=3lLHVyPvTX0
Since you are at it, cabin air filer is way more "fun" to do. www.youtube.com/watch?v=GFru88RczyI