When is a Project(.APRX) too big?

[graharg_MAO]

When is an ArcGIS PRO Project too big?  What is your practice on managing the theme, complexity, connections and purpose of project files?  I have practiced limiting my projects to themes and AOIs but Then I end up with many projects with few maps and a few projects with many maps.  I am sure there are limitations, but I have not hit many.  When the project gets slow or off subject I start a new project.

One measure is the size of the Display Cache.  I do clear the cache regularly when performance becomes an issue .  I also frequently clear the %TEMP%