Is the copy with mates usually a slow process. I am copying a fastener into an assembly with two mates, I insert four instances of the part and it takes my computer around 20-25 seconds to populate the fasteners. Is this normal??
Generally its not a "fast" or instantaneous process. Just like the first time you select to make a new Reference Plane, the menu takes about 3-10 seconds to appear.
So it is normal, unfortunately. I have seen this with 2014 and 2016.