The only issue with length should be signal interference. In 2002, we designed a remote "runner" mouse for our robot, and it had about 30 feet of cable running to it, with power for a motor, and a signal cable for a steering servo. With the long cables running right next to each other, the motor power cable would interfere badly with the steering of the servo, so we switched to shielded cable for the servo, and it worked fine.
Here's one of the
photos of the runner.