In all honesty, you're better off with OEM and changing every 10k. With the lifetime ones you have to regularly clean and oil them.
Mine made +7bhp over a standard GTI on JKM's dyno with a K&N panel filter. Not an exact science as different cars, but how often have you seen a standard car make more than 197bhp at JKM's? I know I haven't. . .
Nick @ R-Tech noticed the increased flow from the filter whilst mapping it.
You get a little more intake noise, improved throttle response also
Generally they require a clean every 20-30k miles.
Great little mod for £30