20 foot long speaker cable: is it ok?

I am far from being an expert so I pick up on odd comments. Did I hear correctly that in theory a longer power cable is better than  a shorter one?
It was explained to me at the time but I didn't retain the reasons

I used a 20ft pair of Mogami 2477 Blue Neglex OFC coaxial with my KLH Nines for 23 years! Excellent sound, never felt the need or urge to change! The cost: $1 a foot (dealer accommodation)!

tatyana69. That very question was asked over on Audio Asylum.. Sadly no one answered. I used to be in the ’long is better camp’... mainly because I was using long 3 or 4 meter PC.. LOL
Now I am in the buying shorter is better since I have been buying shorter PC cords 1 meter, 2 meter. The whims of fate...So currently I have a mix of long AND short power cords, same makers. Difference? none I can hear. Big differences in current vs older models of Pangea in particular. The ’original’ AC9... Throw them away (they just sound muffled) Ditto original AC14. The original AC9SE. AC14SE are better, and worth keeping for odd stuff. In fact they are great to help ameliorate digital grunge affecting amps and preamps.The latest Pangea Signature are pretty good PC.I have also made DH Labs AC wire ($8 ft stuff) with Furutech Rhodium '28' series plugs and have two of those in the system. One 2m the other 4m.

To almarg:

Of course capacitance will affect the sound.  Capacitance impedance gets less with increasing frequency or capacitance = 1/jwC

This means the higher the frequencies, the more it will feel like you are SHORTING the cables.  Although in most cases this may be negligible, it may have the effect of losing high frequencies the longer the cable. 

The shorter, the better. however it is up to your gear: amp. and speakers.
Give me the bran and model and I'll let you know what guage you need for 20 feet.
Keep in mind that speaker's cables resistance double, as it goes (red) and retunrs (black). So your 20' is actually counts as a 40' cable!