I put about 49,500 miles on my original Goodyear Fortera HL Edition tires from the factory. I would have likely gotten about another 10,000 useful miles out of them because they still had about 6/32" of tread, but decided to replace the entire set rather than having uneven tread depths when one was sliced by a knife (or something sharp and shiny) on the road. They have 11/32" when they are new, so tread wear would have projected to about 60,000 useful miles at the 5/32" tread depth.
The Hankook Ventus AS RH07s, which replaced them, currently have about 23,000 miles on them, and they have about 9/32" of their initial 12/32" tread depth left. This would project to about 54,000 useful miles at the 5/32" mark, which would mean that they are wearing a little more quickly than the original Goodyears.
BTW, I use 5/32" as the limit of useful tread based on typical weather condition requirements where I drive. Reliable sources indicate that tires must be replaced by the 2/32" mark, but should be replaced by the 4/32" mark if rainy conditions are often encountered, and 6/32" if snowy conditions are often encountered. Since I drive on snow covered roads only a few days each year, I figure that I can push the tread wear limit a little beyond the 6/32" recommendation.