Every connector has a little voltage drop associated, so the servo will see less voltage and that means less power to the servo to do it's job. Probably not a big deal in your case.

More of a problem, more connectors are more places for failure. Unless you're using gold-plated connectors, it's more places to corode and cause the servo to act flaky. If it was me, and I needed the plane set up now, I'd cut two extensions and solder them together, I might even cut the connector off the servo and solder the longer leads in, removing as many connectors as possible. However, I trust my soldering, and you'd want to avoid having the wire unsupported and flexing at the solder joints as thet can break at that point.