I think it largely depends on if you're connectors are single ended (RCA), or balanced (XLR). If you're running RCA IC, then you probably want to keep them at 1M or 2M. For XLR, the length becomes more irrelevant.
length of interconnects for passive preamp
I understand that when using a passive preamp short interconnects are recommended. I have two questions before I purchase them: Does that short length requirement apply to both the ic between the source and passive as well as the passive and the amp? And regarding the length itself, is the shortest always best? I see that some companies offer a 1 foot or even 6" length - which I could use, although it would require some serious rearranging of my equipment; but will those very short lengths provide a noticeable improvement over a 1.5 meter or 2 foot ic? Not sure if there is a rule of thumb. Many thanks!