Long time listener, first time caller. Jumping right in. I am curious how to tell where a filter is at in it's useful life. I change oil on a few semi trucks as well as my own person pickup and I noticed when I pull the filters off these trucks that have been sitting for a while, the filter is only partially full. We buy quality Donaldson filters so I wouldn't think the ADBV would be the culprit. Also they are all vertical mount with the o-ring to the sky. I'm wondering if this is an indication of where they are at in their service life.