How long does a cable need to be?

No, not speaker cable, I think we've done that discussion! What I'm mainly thinking of is interconnects from source to preamp, and preamp to power amp. Naim have always been quite inflexible in this respect, despite the chagrin of many who have tried to get their cable dressing under control. The same could be said of mains cables too. So I'm curious, given Naim's reluctance to offer a range of cable lengths, especially short ones, about why this might be, and what principles of electrical engineering might lie behind this. OK, I'll be honest, I probably won't even understand the electrical engineering principles, but it would still be nice to know that they were judiciously applied! 

If you have a smallish rack, you will no doubt have noticed that keeping cables neat, hanging free of the floor, not touching each other etc., is severely hampered by the fact that most of them are twice as long as they need to be. A quick glance at Chord's website shows that even the DIN cables they produce almost exclusively for Naim users are available as standard in slightly shorter lengths than some of the Naim equivalents, with 1m versions available (but not the 0.5m lengths in which they supply their RCA cables). So is this a DIN vs RCA thing?

Finally, I've noticed that some manufacturers of passive preamps such as Townshend suggest that these leads should be as short as possible, especially between source and preamp. So what on earth happens if you want to run one of these between a Naim source and power amp? Maybe you get burnt at the stake for suggesting such a thing, but if Townshend say that you should use a mere 300mm lead if it reaches, and Naim will only sell you a 1.25m one, what principles should guide your decision?