What kind of company can realistically expect people to stay that long anyway? There are always going to be people who are lifers at any job you go to, but there will also always be people that leave for one reason or other. Seems silly to discount an older person because they might only stick around for ten more years instead of 30. Even a full on company man that bleeds the company colors is more likely to change jobs, or even careers, the younger they are.
I could argue both sides of the coin I guess.