Length of speaker cables

I use Audioquest GO-4's for my Vandy Treo's and Ayre monoblocks.
The length is 6 feet.
My dealer, John Rutan, swears by short speaker lengths (As does Ralph Karsten (atmasphere). Anything longer introduces/enhances cable artifacts.
I don't know what your system is besides the AQ cables, but if you have 'good' equipment, and some disposable income, I would suggest buying a pair of AQ William Tell cables.
I heard them at Audioconnection and the difference between the GO-4 and William Tell was amazing- and I am not a cable nut. 
They were truly cleaner/clearer. Even the bass was enhanced.
Like I said, I am not a cable enthusiast, but those cables were absolutely amazing. Yes, not inexpensive, but, in my mind, worth the cost.
Bob

millercarbon 

Just to be clear steven0713 when saying you will definitely hear worthwhile improvement with quality cable I mean quality cable, not that 4s11 stuff. You can spend a lot and still have crap if you're not careful.

The Canare 4s11 is worth trying out.  The poster quoted above is known to be a fanboy of certain brands (only those he owns) and has difficutly seeing beyond them.  When he mentions spending a lot, that is true, if you consider spending $81 dollars for a pair of terminated 6' Canare 4s11 from Blue Jeans Cable a lot.

shorter better than longer all else equal for speaker cables

As said by @jjss49 , shorter is better, all other things being equal. It means less R, L, C to interact with the speakers. So, I suggest you try to borrow a shorter set of cables or buy them with right of return.

Many who go to monoblocks use very short cables, a meter or less. Possible in your case (at least for comparison)?

Both parts of "audible improvement" are hard to predict in someone else’s system; i.e., whether the difference will be audible to you, and whether you will think it an improvement. Not all differences make the sound better or worse.

One of the benefits of switching to mono blocks is the ability to use shorter runs of cable. It is not imperative that you take advantage of this opportunity, but why wouldn’t you? This is an excellent time to upgrade, If you are going to use the the same AQ cables in a shorter length, you will probably not notice a difference. Use the shortest length of upgraded cable possible; it will look neater, impress your friends, and sound better. While you’re at it, replace those standard power cords with some better ones. Enjoy!