I typically buy new luggage every couple of years, usually a different size, so they end up lasting about 5-6 years each. That said, I usually take 30-40 international business trips per year. When you travel with suits, it is best to find one that helps fold them nicely and keep them folded moderately tightly while in transit. Unfortunately, my favorite model isn't made anymore, though I keep a lookout for similar models. Probably the best built model I have is a 22in Tumi that my wife bought for me for a birthday or something a few years back. I still have it, and it is in great shape. However, it was very expensive. I still have a few years of heavy travel left, so I'm considering getting a mid-size Tumi, if it holds suits well. When we go on vacation though, I never use the suiters, just a big enough suitcase to hold the clothes and DWs souvenirs.
Final word of advice: if you fly a lot, remember that weight limits. The large size suitcases will easily go over the limit even when not expanded. Whenever we have actually unzipped the expansion compartment, we have gone overweight...better to go with 2 suitcases instead of one expandable. Also, when you fly (if you buy souvenirs) it is really a good idea to have a handheld luggage scale to make sure you are within limits. I never need it on the business trips...but when we come back to Japan from Hawaii, look out!
R