I'm trying not to get sucked into this, but there comes a point when I must. Line arrays do not posses magical or mystical properties and in fact they can be a poor choice.
You are incorrect about fatigue being just a matter of volume. The design of conical or point source makes a dramatic difference. The fact that you don't have the issue is a tribute to your personal skills that are not possessed by the majority. The line array properties are very forgiving to the ignorant or forgetful.
Here is one of the major problems with a line array -
Near field there are huge phase problems between the top/bottom speakers, and the middle speakers, vs a point source (i.e. traditional loudspeaker).
You can electrically correct (time delay) for only one distance. The above is exactly why they should be placed as far as possible from the audience - they usually should be setup behind you.
Next is the problem of excessive horizontal dispersion in small or narrow rooms, which leads to too much reflected energy off of the side walls, further diffusing the sound.
A
properly designed point source loudspeaker can often sound superior - and I hinted at it back in the "Is that Bose?" thread. What is that? It is easier to describe what is not a properly designed loudspeaker, because there are so many of them. IMHO, absolutely nothing has more tarnished the public's perception of "DJ sound" than the typical two-way 15" loudspeaker. Nowhere in the high fidelity/audiophile world will you see 15" drivers crossed over to mids or tweeters above 500 hz, yet it is rampant in the DJ industry. There are those here who object to the physics behind this, so I won't go into the "why" (they certainly don't act like a point source), just let me say that,
especially at higher volumes, most of them do not sound good, leading to listener fatigue (DSP on newer models has helped, but it can only correct for so much). I have been at far too many weddings (as a guest) when it was off to the bathroom for tissue paper to stick in my ears, when the DJ started cranking it.
No wonder the name "Bose" influences people, but just because a Bose line source speaker might sound better than a
poorly designed conventional speaker does not mean they are a panacea for all situations. They are just another tool in the DJ's arsenal.