Aircrew should only eat food which has been properly prepared. FL350 with 4 hours to go is bad enough, but getting the !!!!!s at 250 feet in a Herc would be less than amusing. So no, you certainly shouldn't bring your own !
Never did see the point of 1-3 or 3-5 hours rationing myself..... But 5-7 and more, indeed yes.
The stupid S1 box was a load of absolute cack when I stopped flying in 2002. Are they still as bad now?