Welcome to the forum, Phong.
I am going to suggest that you have some very intricate dependencies between the part models and the assemblies. There is no reason for a part to regenerate unless top down dependencies exist at the assembly level. Managing dependencies is a critical element in keeping Creo interactive.
The same is true for regenerating parts. There are a few operations that can force an entire regeneration of the part such as changing parameters/relations, but for the most part, it picks up from where the change occurred or the feature is affected. Two things that really lows down part regeneration that I have found are round features and merging of solid bodies (typically pattern count solid features).
Most of the time, computing power will make this process seamless. I use a laptop so I do notice these things. What I find more annoying is that not everything regenerates the 1st time around, but that's another topic.
I don't know if there is a means to delay regeneration. For your case, maybe external simplified reps can lighten the load to some extent by only working with the features you need for your analysis.