[Andrewwelton]

I think its a load of crap personally, I've never flashed back to stock, and I've never flashed more than once, and I've never had a problem... Whatever floats your boat.

But the people over at xda, if I remember, one of the people stated (this is as word for word as I can remember) "It is common knowledge that bits get stuck on a ROM chip, so flashing multiple times ensures that all stray bits on the ROM chip are cleared and you have a bug free experience"

But as I said, I think its a load of crap lol.