K&N recharge kit, available at all good online stores
Supposed to last ages between oil refreshes, I remember at least 50k miles. I did mine once (i meant twice in about 7 years) every 3-4 years at around 30k I think. Never that dirty.
Personally I wouldn't touch it unless you think it needs doing, I wouldn't do it for maintenances sake, easy to over oil it.
K&N recharge kit, available at all good online stores
Supposed to last ages between oil refreshes, I remember at least 60k miles. I did mine twice every 3-4 years at around 30k I think. Never that dirty.