Ed, if you injected the salt brine in the meat, you may end up with a really salty brisket. Brining is more of chemical reaction with the surface protein molecules in the meat, and is not meant to flavor the internal meat. The purpose is to trap the moisture in the meat. The exception to this is a curing brine for ham, where you do want the curing salt to penetrate all of the meat. Let me know if my suspicion is right or wrong.
As for 3 days in the fridge, I don't think that's necessary at all. Again, that's due to the salt in the brine. A rub, with salt in it, and a low-salt injection could probably stand a couple of days, but I don't think any more than 12-18 hours is necessary (maybe not even that long).
Just my 2¢!