I never ever travel with a bag larger than 25 inches, even on long trips to multiple climates. That size bag is much easier to manage while on the trip - in and out of buses, trains, and taxis. No matter what the length of a trip, you don't need more than 6 outfits as long as you plan correctly. That amount of clothing plus two pair of shoes will easily fit in a 25-inch bag. Last week I packed that much stuff in a 20-inch carry-on.

It might be a different story if you're going diving in Antarctica, for anything else stick with a smaller bag.