Note: I own an older version of this bag so my experience may be different from yours. When I set the intention in June of 2010 to go on pilgrimage to India/Nepal, this was the first thing I bought. It took another 18 months to actually go on the trip. This bag mostly survived. There were four "failures":
The wheels began to seize up by the end (the biggest issue).
The compartment divider began to tear.
The duffel strap handle's Velcro became largely useless (as you might expect) so the straps just flopped around (annoying).
The zipper pull for the backpack tore off. I could still use my fingernails to open and close, but switching between backpack and roller is something you tend to want to do quickly/easily. I used the backpack feature less because of that.
The top handle was close to failing. That would have been a disaster if it had happened.
Not too bad given all the plane/train/subway/bus/taxi/walking and over-filling. If I were to improve the bag, I would do the following:
Ditch the duffel straps. No one's going to carry this giant thing as a duffel and the straps just became a nuisance. The only reason to have the straps is for porters to carry it as a backpack...but it IS a backpack!
The expandable feature is pointless. Never used it. Bag's already too big. I suffered overweight fees on a couple occasions. The limitations of a 28" bag would have kept me out of trouble (just buy another bag for all the stuff you purchase).
Design better wheels. This may be unfair to expect given the terrible abuse the wheels took.
Stronger zipper pull for backpack feature.
If you plan to live out of a bag for 6 months traveling developing countries, you could do a lot worse than this one...but you could also do better. I'm considering going back for another extended trip and I'm looking at a Briggs & Riley Expedition 28. Much more expensive, but lighter and extremely well-designed/built with a lifetime warranty.