It seems that in the life cycle of a pair of trainers, blisters occur at both the birth and the death.
I'm often stricken by blisters as I wear in a new pair. But this soon fades as my feet take on the shape of the shoe (rather than the other way round, which am sure would be preferable).
Today, I discovered that as the shoe wears out, blisters re-appear. Fortunately I was able to rip out most of the 'padding' that was causing the problem before I bled too much over my socks.
I think it might be getting on for time to invest in a new pair of shoes.
[Image credit: Rich]