Brakes problem
2000 BMW 528 6 cyl Two Wheel Drive Automatic 99800 miles
----------------------------------------------------------------
Once the Brake warning light comes on, how long do I have to change brakes before I cause damage.

Also do I need to change the Rotors too, if I changed them last time ?

There is a safety margin that you have that is possibly one to two weeks, depending on driving habits. Discs are consumable and may or may not require replacement, you must determine this during the discovery phase or your repairs.