I just realized that I've had my current pair of running shoes since April 2009. I was just beginning to run again back then and didn't really start attacking the miles until around August. The shoes also got a rest from mid-September to early November after I twisted my ankle while in Norfolk.
But I figure that I've covered 450-500 miles in them, and even though they don't look all that bad, the guidance is to retire them between 350-500. Frankly, I'd simply be following protocol since I see and feel nothing wrong with the shoes yet. I'm not suffering from any ill effects due to cushion breakdown, and other than some non-hurting blistering between some of my toes (which I think has more to do with damp socks and increased mileage than with the shoes) my feet are feeling fine.
I've been running in cheap Saucony's which, to me, feel a lot like the less expensive ASICS. So I'll probably keep on the lookout for another pair of the Grid something-or-others on sale. I'm not, however, going to switch up my shoes before the Carlsbad Half Marathon. I want to introduce as few variables as possible on the eve of the race.
I'm re-tackling the long 12-miler that I quit on last week. I ran lightly today, staying well within my aerobic training zone, just to stay loose, burn some calories and meet my weekly mileage target. I feel good, and with a good night's sleep I think I should be able to finish the course and have strong confidence on my readiness for the real thing two weeks from now.