This is most likely caused by wave links or interpart expressions that need to be updated. You can delay updates (interactively or with code) until later. Loading all the components then doing one large update might be faster than multiple updates during load. The delay update option is usually found in the tools menu (or use the command finder).
Would setting these ON, in the Customer Defaults help?
"Delay Part Module Update"
"Delay Product Interface Update"
"Delay Geometry, Expressions, and PMI"