I have a assembly that has 350 mates and around 150 components. I have "Do not rebuild when switching to assembly window" checked. When I open a component in it's own window and then return to the assembly it takes a good 2 or 3 minutes for some kind of calculations to happen. I don't even need to change the component - just open in a new windows and then return. What is Solidworks doing in this time if it is not rebuilding? Does anybody have an tips for me to help reduce this time?