I have a pair of Alex DH19 rims that came stock on my Redline Monocog 29er. I have about 8000 miles (or more) on them with no trouble, aside from requiring a minor re-truing during the first tune-up. Based on the indicator line, I would estimate that the front rim has been worn no more than half way through its serviceable life by the rim brakes.

I have been very satisfied with the rims, but not so impressed that I won't consider other models when the time comes to replace them.