I have always run my fell shoes until they start falling apart (I wear Innov-8), i.e when they develop tears,splitsin the midsole or hole. This can take a long time for me as I'm pretty light.
I recently heard a podcast where it was suggested that the shoes go in the bin at 400-500 miles even if they look fine as the cushioning is shot and your more likely to get injuries etc.
Whats the general feeling, do you chuck your shoes away regularly, or wait until 'they've had it'?
Should add that although this may be less of an issue with fell shoes than road shoes, I like a but of cushioning due to my ITB.
Thanks for your thoughts in advance