Thanks for the feedback and links. I did run across the luggage lockers in MSP in an online search for luggage storage options at MSP, and yes, it looks like they clean out the lockers after 48 hours.

Another option that I will try pursuing is looking for a nearby hotel that will store my bag for a week. I plan to stay one night prior to my side trip and can fit in another night after the completion of my side trip at the same hotel property if necessary. Anyone with any ideas as to which of the airport hotels will/might keep a bag for a week under these conditions?

And, as course, as a last resort I can always lug the extra suitcase along with me on my side trip.