EPDM tube resistant to ozone on the long run?
The problem with EPDM is that it has tertiary carbon sites (and some double bonds for cross-linking). Forget the latter as let's assume the material is already cross-linking.
Normally carbon backbone polymers with substitution need anti-oxidants to prevent the C-H, where there is a side group, from oxidising. These delay the oxidation process and define the lifespan of the material. So after time, the anti-oxidants will be consumed and the polymer will be prone to oxidation, which leads to fragmentation. 
Ozone is a great oxidant as you know. When we used high pressure ozone,  we always used fluorinated everything. By using fluorine saturated polymers, there's no sites for oxidation to occur.