Originally Posted by tennesseean_87
My understanding (someone correct me if I'm wrong), which reading the mashing theory wiki page did not contradict, is that once the starch is converted into sugars (at a certain ratio of fermentable to unfermentable sugars), continued enzymatic activity can continue to break down the unfermentable sugars into fermentable sugars. The article does state that time affects the level of fermentability (ratio of ferm:unferm sugars) because (emphasis mine). You seem to be indicating that once a starch is converted, it's either fermentable or unfermentable and will stay that way, while the article seems to indicate that the sugars can be further broken down, in which case a mashout would help if you are going to do a sparge or pause between mash and boil and want a higher amount of dextrines. But if you are going to begin the boil immediately (no-sparge BIAB), as you said it has no effect.
It depends mainly on the starches. You might get another 1-2% more conversion from a longer mash, but I've mashed overnight for 8+ hours and only got 1% more conversion than I do when I mash for 45-60min. That's really not even proof that it's better, I've done it twice and gotten 1% more than expected both times... but sometimes I get 1% more than expected with a regular mash too.
Lately people are realizing that the vast
majority of mash efficiency is gained in the first 30min of the mash. It used to be people thought that mashing longer led to better efficiency, but that perception is changing. In some cases I've done 30min mashes and hit all my numbers.
Perhaps in a bigger setting (craft brewery) time makes more of a difference due to the huge increase in volume of the mash, but at least on the homebrewing scale I've seen nothing to convince me.