Who applies mulch in a 4″ blanket? Nobody I’ve seen, thats for sure. I know that is what your are supposed to do, but more often than not, it is more like 1-1/2″ t0 2″. I’ve also seen crews just rake on more mulch, not aerate the old stuff or remove it entirely.
If you use good mulch, then you don’t have the issues with bugs or fungii. Shreded hardwood is indeed the best, but you can get YEARS of an application of pine bark nuggets without adding to it. Just turn it once or twice a year. The developers I deal with actually like to pay for new mulch every spring, as it is a really cheap way to spruce up their property while the crews also install spring annuals. It is a signal spring is here.
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Here’s one I did that was planted in ’06 or ’07. Photo was taken last year. Its in central NJ. I was surprised that there was such great (total!) coverage by the ground cover junipers. In this case, the owner really cares about maintenance. They even put up little signs asking people to use the walkways and not step on the groundcover! Its in a slightly upscale area where people tend to heed stuff like that. So often the maint guys just pile mulch on and smother the ground cover plants. The end bulbs are large, so you have a lot of rooting area and snow piling area. All the trees were healthy. You don’t have to worry about snow plow damage with plants like this. Trees in little 4′ x 4′ or 5′ x 5′ islands…I’ve seen so many failures with that detail. Its a tough environment for a tree with all that reflected heat and then the winter snow. The trees often look so sad. Its hard to get them to build them according to detail with good soil and proper drainage. 
