In the overall scheme of things in the audiophile universe, it is pretty well understood that power amplifiers are designed to be load driving devices. Preamplifier and other "small signal" devices are in general not designed to drive loads as a first priority.
A long interconnect cable with its distributed capacitance along with the input capacitance of the amplifier it is driving, can be a pretty difficult load for a preamplifier. A speaker wire is a pretty simple load for a power amplifier, especially in comparison to the really complex load the speaker crossover may represent.
Thus, my thoughts would be that if the preamp is not designed to drive hard loads, one should keep the load represented by the interconnect cable as low and simple as reasonable possible - - short, well shielded, and low capacitance interconnects.
Since the speaker wire probably is not the worse case problem for a well designed power amplifier, I doubt if it will be in trouble driving 10 to 30 feet of decent speaker wires. Of course if the cables are highly capacitive, then all bets are off.
This idea is probably pretty east to test. Simply have two lengths of the same kind of interconnects and speaker wires available, one short pair and one long pair of each, and do some listening tests (preferably double blind) with both combinations, and see if we can really hear any difference. Actually, if you did not mind doing the tests in mono, you could hook up one channel with short interconnects and long speaker wires, and the other with long interconnect and short speaker wires, switch the system to mono, place the speakers side by side, and do instant AB testing with your balance control.
Just an idea and suggestion.
Frank Van Alstine