Do oil catch cans really work??

I'm going to get walnut blasting done on the car soon to get rid of the carbon build up on the intake vales, was also going to get an oil catch can to try and prevent more carbon build up....



But having read a few reviews am not convinced oil catches do anything to prevent carbon build up on the intake vales.



I know all about the 'theory' but have seen no real life proof of someone with an oil catch can installed and actually evidence it has prevented carbon build??



Anyone one got any firm proof (pictures of intake valves post catch can install) that oil catchs cans actually prevent carbon build up??