Depending on how often you make new hires will determine how often you request availability from your staff.
If you keep the request open, any user would be able to submit their availability at any time. However, if an employee submits their schedule and changes their mind the next day or week, you will need to close and reopen the request.
If you turn the request off between hires, employees will not be able to submit their availability. Users can only submit their availability if you have a request open. Employees will be notified when you open and close requests.