Ok, I just woke up so cut me some slack. If you mash arount 145 you get short chain, highly fermentable sugars, right? 155 you get long chain, less fermentable, right. (I know there's some overlap too) So, let's suppose you mash at 145 long enough to get near 100% conversion. Then raise the temp to 155. Its not going to put the short chains back together is it? At least in my mind it doesn't seem likely, so I quit worrying about mash out. The only time I would mash out is if I were trying to get a wort that was not very fermentable, like for a lambic. Then the mash out might stop conversion, if I was using a low DP malt that converts slowly enough to actually pull that off.