For Users with a high number of courses it takes a very long time for loading the course overview, if they click on "My home". Clicking on "View profile" in the navigation block, shows also an overview of all courses. But it's loading much faster.

For Example:

It takes 32 seconds to load the "My home" site for a user with 60 courses. Using "View profile" takes only 1 second.
So it takes much more time for users with more than 200 courses. Using "Login as" to test the waiting time of such a power user, takes also a long time, but then returns no result.