As I always point out, MEC's cycling adisors say not to use alloy racks, but they are doing endless mileage and carrying heavy weights. They say "Aluminium racks are time bombs waiting to detonate."
http://www.mec.ca/Main/content_text....=1170439439852
But the fact MEC has been selling this stuff for 20 or more years in one brand or another, means that they must be holding up pretty well on the average trans canada run since a lot of people do that trip, and shop at MEC. Just keep in mind its' "only" 3000-5000 miles.