The Schedules (loading of the table, detail of a schedule, enable/disable...) get unusably slow when there are 50 or more schedules on a page. How much slow it is also depends on the used browser (Firefox is very slow, Chromium is a bit faster). The Firefox warns that the page is slowing down the browser and offers to stop loading.
Example of times of loading the table:
- 50 schedules ~6s, 100 schedules ~17s, 200 schedules ~61s