PIMPIM, I'm afraid u asked the wrong guy... I didn't mentioned anything about HKS, I think u are refering to JAHAX.
Anyway, since u asked, I think its because sponge type filters tends to harden and breaks into ashes and therefore being sucked into the engine, correct me if i'm wrong Jahax....
i think K&N is ok..

PIMPIM, I'm afraid u asked the wrong guy... I didn't mentioned anything about HKS, I think u are refering to JAHAX.
Anyway, since u asked, I think its because sponge type filters tends to harden and breaks into ashes and therefore being sucked into the engine, correct me if i'm wrong Jahax....
I tried cleaning the Apexi filters with K&N liquid cleaner.. big mistake... .. u can see the filter like squeezing itself in whenever u pull the throttle cable on the engine bay...
yea.. they come with it. and they change it frequently the sponge
how many here change the sponge frequently ?

dean: i dont think u can actually. I tore apart the 'stuck' filter. It's actually like 'paper' like material...