2005 2500 crew cab ccv filter
 

How often should you clean the filter? Has anyone added a expansion tank and connected it to the filter?

The CCV on a 5.9 CTD does NOT have a service interval as itonly a baffled box to help direct oil drips back into the engine while still allowing vapors out. The only reason it would need attention is if it is leaking oil from either the o-ring to the valve cover or where the hoses connect to the CCV. The former leak can be fixed by replacing with a new similar sized o-ring, the latter leaks can be fixed by cutting back the hoses and using a small hose clamp or zip tie to reattach them.

Some people ditch the CCV entirely and replace with a catch tube and can.

The CCV on a 6.7 CTD DOES have a service interval, as it is part of the whole EGR system.