I'm finding some oil wet spots around the check valve of my RX catch can which tells me my side mechanic was correct, a catch can will not catch 100% of everything. I noticed it after switching to full synthetic. My guess is the little bit of oil left in the gases exiting the can is hitting the check valve and a small amount is condensing over time and settling in the bottom of the valve.
My bottom line conclusion: A catch can will not solve valve build-up 100% but it will no doubt help cut it down and make your engine run better since it's not compensating for the oil and moisture in the crankcase gases. However, we still should get a BG induction service performed once every 15,000 miles to keep things nice in clean for the long term.
Of course if you plan on getting rid of your truck at or before approximately 100,000 miles, you probably can skip all of this and just drive it without a worry and eventually unload it.