I should also mention that on the first activation, the attribute resets to 5. On the second activation, the attribute is increased to 1,000.
Also, simply activating the cheat after the attribute resets isn't a great workaround. It's not even a workaround, in fact. The attributes reset rather quickly after the attributes are set to 1,000, so it's fairly common to enter battle only to discover the attributes have reset. EDIT: I need to do some more testing, but I think the resetting happens more frequently when all attributes are raised.
I used Cheat Engine to manually set the attributes to 1,000, locked the attributes at 1,000, and waited a few seconds before unlocking. This method seems to keep the attributes at 1,000 for a brief while longer than the trainer's method. However, they will still reset.
FYI: You can use UE Explorer and Gildor's Extract tool to check out the AGOTGame.u classes. I don't know if that will have any value to you, but it eliminates the "is it an int? is it a float?" guesswork.