Longer is better?

That’s what she said

Did you ask him why he said that?

@thecarpathian as follows are his words right after he told me my existing cable was “hideous” and provided poor sound without asking me what I thought about my sound. “For instance, we always try to persuade our customers out of getting short digital cables (less than 1.5m), they don't sound as good as a longer version of the same cable. Regardless of manufacturer, short digital cables sound less coherent, less focused, and less spacious than a 1.5m cable (optimal length). Even if you must coil up the extra length, a 1.5m will outperform its shorter siblings.To put this a different way, a 0.5m sounds like a local bar band; they know all the notes, they have enthusiasm, and the gist of the song - but just don't have quite the skill, experience, or the best stage gear to make it sound great. A 1m sounds like a successful cover band, more familiarity with the material, bigger sound, definitely higher skill level, and better instruments too.  The 1.5m sounds like the band that wrote the music and cut the record; easy and effortless, they've been joyfully playing together for years and have an unmatched, relaxed musicality and coherence. A 0.5m digital cable is sonically compromised, sounds clipped, aggressive and washed out - shorter is worse.

OK  not too short and not too long then. Good quality a must. 

"Ok literally had a retailer tell me I should want a longer digital cable (USB to be specific) vs a shorter one."

@rjduncan - In the case of a USB cable, your retailer is misinformed.  He is likely referring to the belief by some experts that a length of at least 1.5M is optimal for digital S/PDIF cables, and mistakenly applying that to USB cables.  Most successful salespeople are good on the people side of things but not all of them are as strong technically.  Just being ignorant of technical information does not necessarily make the retailer a "sleezball salesman", even considering all of his flamboyant hyperbole.