Appeon Performance Tuning Guide
Technique #2: thin-out “heavy” UI logic

Frequent triggering of events such as Timer, MouseMove, and SelectionChanging slows down performance. For example, once a Timer event is triggered, it occurs repeatedly at a specified interval that can be set to even milliseconds (1/1000 of a second). Minimize the usage of events with high repetition such as Timer, MouseMove, SelectionChanging, GetFocus, LoseFocus, Activate, and Deactivate.