if your stock any *should* be ok. but alot of it has to do with traction more then any thing else. if your on a drag strip with slicks and u have more the stock hp and you launch its not going to take much before the 7.5 gives up. if you on the street and you launch it with like good street tires you should be ok for a long time.
its not the speed of the parts turning that will kill the rear end its the "shock" factor, if you take off at 6k and the rear tires just spin its not very hard on it cuz the parts are just turning, however if you take off from 6k with NO wheel spin at all and just GO the rear end will have a massive shock to it and will break lol, pretty much the stock 7.5 rear end on street tires will be fine, if you go to the track and drag it alot it will eventually break, but will last a while (if the install was good and the parts were new when you installed them)
Right, there is a misconception the the 7.5 is very weak. It's not! It's actually alot stronger than what people think. Brandon is correct about the dragging and everything. The 7.5 will take you to and from the track, but not on a daily basis with slicks on the car.