Running shoe life span

my feet tell me when mine are on the way out, its usually at 6mnths (doing 20-25 miles a week ).........The ball of my foot and my foot starts to roll out.....and aches.Gone off asics for this reason and trialling a nike shoe and saucony trail shoe at the moment, hoping one might suit me better.

I wear mine until they don't feel right any more.  If I avoid bumpy pavements because I can feel the bumps through my trainers, I know it's time for a new pair!
Suzanne, what Asics did you have that problem with?  I just had the same thing with Nimbus 12s and have replaced them with Nike Pegasus (I loved those Nimbuses, I really did.  I just didn't love the new model).

The best thing I find is buy another pair, and try them out (I use the same type so it's not as daft as it sounds) when the new feel significantly better then the old, I'll swap, it's difficult to tell when the old have worn out to the point it will cause you harm