For in park discounts (merchandise, dining) - immediately, as all you need is your id.
For discounted tickets (10% off) - immediately, purchase through Company D.
For travel discounts (resorts) - once you have access to the Hub.
For free Guests admittance (main entrance pass) - 2 weeks after first ojt day.
For Cruise Line - 3 months following Traditions.
For Comp Tickets (seasonal/CP/PI never eligible) - distributed in summer and winter, must be employed before tickets are realeased.