Performance Issues

If your MagicMirror run on PC class, there would be not any problem for performance.

But If you are using Raspberry Pi, overflowRolling:1 with such a many calendars and events makes your system severely slow or freezing. Especially in month view, you should try carefully. I recommend you don't use overflowRolling:1 in month view on Raspberry Pi. In other views, use it carefully. If there are too many events in a view, you'd better control your number of events and calendars. You can also hide overflowed events with overflowHeight or modifying custom.css.