Max length of IC's? Long IC's vs short SW

Regarding your general questions, there is no universal answer. It is all highly dependent on the impedance characteristics of the specific components that are being connected, as well as the parameters of the particular cables. See this thread.

In the specific case you are asking about, unless your components or speakers have extremely unusual impedance characteristics it would seem very likely that taking 20 feet off of the speaker cable length, while adding less than 8 feet to the interconnect length, would be the preferable alternative.

Regards,
-- Al

I made a set of bi-wired cables for a client 75 feet long and he loved them.

Thanks for the advice. Any one know what's the max you can go with unbalanced IC's before you run into problems? Can I go 12 feet or should I try to do everything possible (unlikely) to get down to 9 feet? Thanks.

Most IC's have a spec for capacitance per foot. Longer IC's=more capacitance (generally means that the treble will be rolled off). Look for cabling that has low Capacitance per foot as far as IC's go.
Also, unbalanced cables are prone to picking up noise that you will be amplifying along with the signal from your source.
Speaker wires will have a much higher level signal moving through them, consequently a higher signal/noise ratio.

Any one know what's the max you can go with unbalanced IC's before you run into problems? Can I go 12 feet or should I try to do everything possible (unlikely) to get down to 9 feet?

As I indicated in my previous comment, there are no universal answers. The likelihood that a long unbalanced interconnect will work well depends on the output impedance of the component driving the cable (the lower the better), and the capacitance per unit length of the particular cable (the lower the better, as Ths364 indicated).

There are numerous other variables that can also come into play that are normally either unspecified or unpredictable, which makes it impossible to make a specific prediction even taking into account the specific component impedance and cable capacitance.

Your chances of success with the longer length may also be helped if you are able to have the AC power cords of the two interconnected components plugged into the same power strip, duplex outlet, or line conditioner. That will reduce the likelihood of ground-loop issues, which having long unbalanced interconnects can sometimes contribute to.

Regards,
-- Al

Most likely the long unbalanced interconnects must be shielded(RFI safe) and it dictates higher per-unit capacitance. How much of the trebble will be rolled off? Probably not too significant. May even be more beneficial to the listener, but I 'grew up' from having unbalanced interconnects and use only balanced between components regardless of distance.
I can share on how to convert any unbalanced component to balanced.