This has crossed my mind recently, especially with the cruddy shape the PCV valve was in from the breather chamber on my Civic.
Other than 'seeing' visible holes in the hoses themselves, I tried spraying some MAF sensor cleaner(what I had on had so you know lol), at various vacuum hoses; primarily just where they connected to another location(IM/eblow etc), and I didn't notice and changes in idle.
Does that mean the hoses are good/no vacuum leaks at the hoses I was able to spray and visibly see? Lastly, how tight do those 'spring clamps' need to be on vacuum hoses? Just enough to prevent it from moving, right?