Help my shoes crumbled apart!

I recently took a pair of +/- 3 year old Green Cross summer shoes out of the cupboard to wear on a shopping errand. The shoes crumbled under my feet as I started to walk along the pavement. A very pleasant lady at Customer Care explained that the soles were made of polyurethane foam which has a limited life span due to hy****ysis of the material over time, and that in order to retard this process you have to wear the shoes regularly. She advised me to return the shoes to the shop where purchased and they would decide how to handle the complaint. There was no assurance regarding repair , replacement or refund.<br> <br> I thought that the hy****ysis explanation was a little far-fetched but after some internet research found that the problem with the material is well known (including brands such as Tsonga, Froggies, Nike etc).<br> <br> My objections i) why is there no warning at point of sale that the shoes have a very limited life span ii) how can a customer be expected to wear summer shoes in the Cape Winter (vice versa for winter shoes) iii) why is the buck being passed to the shop when the issue is down to manufacture and materials used.<br> <br> I certainly will not buy this brand again