Length of speaker cables

Make it shorter, it will be neater.

For whatever it is worth, my speakers' instruction manual says to use as short of a cable as possible. I doubt the difference in you cutting yours in half would be audible, but less mess cannot hurt.

I upgraded my 6’ Audioquest Rocket 88 to 8’ Audioquest William Tell cables. Absolute night and day difference. 

careful with the mono block argument for shorter speaker cables... unless you are moving the speakers closer together you are replacing the span with interconnects to the mono blocks - that may well be a losing trade... making a smaller signal travel farther

balanced ic’s often a solution in this case, but then you get into whether the equipment is truly balanced or just having xlr plugs instead of rca

as usual, all else equal is the key phrase... it rarely is...

The shorter the better but with wires thicker than about 10 awg, noone will be able to tell the difference, unless you are a superhuman spectrum analyzer.

Well, here's a marker.  My cable run is 30' with Transient cables and their booster at the termination to the speaker.  I must be such a cave dweller!  They sound good to me.