Does knolling help or is it just part of the fun? When building a new set, many people knoll their LEGO bricks before beginning the assembly. 

My question is: Is there a actual advantage to knolling all the pieces or is it only a way to stretch the fun?

It seems to me that if the main advantage is to save time when looking for the pieces, knolling nullifies this by demanding an enormous amount of time to pre-organize all the pieces.
Knolling is organizing objects by type, at right angles.

If you enjoy spending your time doing that, then by all means, do it.

However, logically, it is obvious that precisely organizing objects provides no benefit to anyone whose mind doesn't require strictly rectilinear organization of objects. 


First, you have to sort all the objects (in our case, lego pieces) by type and colour.
You have to precisely arrange them.
Then, you build something, using up those pieces you just placed so precisely. Presumably you'll knock some askew: do you re-knoll? Do you have to move slowly and more carefully to avoid accidentally knocking them around?
By the time you're done, you're left with a creation, and a small number of knolled spare parts, now no longer in any kind of suitable arrangement (due to most of the parts being put on the model.


Or, consider the other scenario:
 1. You just open the bags of parts and pick from the bags (or, as I do, you dump the bags into shallow containers, so that it's easier to see and grab parts, but you don't mix all the bags together.
 2. When you're done you have a bunch of empty containers.

The advantage to the 2nd way is that you don't have to spend any time categorizing and sorting parts. You just grab what you need.

The only practical advantage to knolling is that you can easily see where parts are, and grab the appropriate ones. You can even count them and compare against the set's inventory to see if any are missing. However, you can achieve the sorting goal without knolling, but rather just by separating the parts by type and colour. This is faster, because you don't waste time fastidiously placing things at right angles.

For most Lego kits, I'd argue that even sorting the parts is a waste of time, because the parts are generally not randomly placed in bags. Even if the kit doesn't have numbered bags for different stages of the build, the pieces are not randomly distributed between bags and so you can still easily find things. (If someone else is sorting for you as you build, THAT can save time, but it requires two people, and thus doesn't really save time overall).

When building from your collection, if your collection is sorted (as mine is), knolling or otherwise arranging parts is a big waste of time. It's fastest if each bin of your collection has one type and colour of part and the bin is large enough to hold the pieces loosely. If (as I do) you run out of space for loose parts, you can save space by attaching the pieces together, or fitting them in tightly like a puzzle. This takes an enormous amount of time and, furthermore, wastes time later when you take the parts out to build. The only reason I put up with it is that I don't have unlimited budget and storage space to buy the bins I use for storage.

TL,DR: knolling is organization taken to extremes. It's based on aesthetic principles and not efficiency. What efficiency it gains can be had for lower cost by simpler organization methods. If you enjoy knolling, go ahead, but it certainly isn't really helping. If you can't stop knolling, you might be OCD.