I changed my wheels for Mavics a couple years ago, but now want to take out my original wheels with some different tires and swap the wheelsets back & forth depending on the type of riding I'm doing. I'll be installing the same type of cassette on the old wheels that I use on the new ones (Shimano 105 12-27T).

My assumption is that I can swap the wheels around without having to do any derailleur adjustment, or at most just a minor tweak on the barrel adjuster. Is this correct? Everything's machined pretty precisely in that area and I wouldn't expect any significant variance.