So far, I've been swapping tires. If my bike was new or at least newer, I might more quickly consider a second set of wheels but a new rear wheel will have a new cassette on it which means that it will be "out of synch" with the wear and tear on the current chain so I would want to change the chain which would then be "out of synch" with the chain rings and they too should be changed so it would be an expensive proposition for a 9yr old bike.

With regard to packs, I would expect that my current rack would fit a 29er so I am not concerned about that. My ride out to camp is a bit of a fitness ride in that I am bringing only myself (and water to drink along the way) but my gear is either out there or coming behind me in the car driven by my wife.