As I mentioned in a previous post, I use allot of sketches in order to obtain certain dimensions for use in my part lists. I try and use sketches from part features most I can.
These sketches are unused in any features so instead of continually having them in face, I make them invisible.
The thing is once I save and reopen an assembly that does not contain sub-assemblies, these sketches will correctly remain invisible.
But when I open an assembly that contains sub-assemblies that in turn contain invisible sketches, those sketches are all of a sudden visible. So much so that sometimes I can't see my current project.
I have become accustomed to first hitting F10 every time I open something.