In Stock and 19T its no problem re running packs as long as they cool off all the way before you charge again. You really don't get more punch on the second run with GP cells...they are good every run...lol!
In Mod you beat up the cells so bad you should only run them once a day. If you have to re run I have heard that a 3 hour rest is a good idea between runs. You want to give the cells chemistry time to stabilize.
What I run: Schumacher Mi5/Associated RC10R5.1/Associated RC12R5.2/Futaba/HobbyWing/Team EA Motorsports/BSR Racing
Where I run: Florida Indoor R/C Complex/Thunder Racing/Florida On Road State Series