I'm running Creo Parametric 4.0 and I have an assembly that's 5-7 parts. I have noticed something when it and larger assemblies open. The message log shows:
Performing analysis........... xx%
Refining analysis............... xx%
What is this analysis and why does it need to be performed?? I don't remember ever asking it to run an analysis when I open assemblies, and it seriously slows load times. Is there an option that is mistakenly left on?
Look to see if there are any analysis features in the model tree. The only place I remember see performing and refining % is during the creation of a shrinkwrap or a merge feature so you may want to look in to what other types of features you have in your model.