As long as your EID is still active with access into GlobalSource and your hotel still considers you an employee, your discount card and any authorization forms you issued are considered valid. One of my agents is on call and generally only works a couple of days each month and occasionally has several weeks or months in between shifts. She has had no difficulty using her discount card for employee rates and is one of the main reasons she sticks around as being on call.
If you are not an active employee at the time of travel, you run the risk of your discount card being invalidated as soon as your HR department strips your access away from MGS or you’re no longer statused with the company. The discount card is validated at the time of check-in.
Worst case scenario, your rate is adjusted from Associate Pleasure to Regular. Best case scenario, they forget to take away your credentials and your discount card is still valid. You can always have a friend look up your discount card on Marriottforms.com to check its details.