Slab
Occasional Tour Caddy
I'd say you have passed that tipping point with those distances frequency, very diligent . In terms of benefits, you are looking at protecting your body, joints etc more than improving times. Prevention better than cure.
See what you've done you bad man!
My current trainers need replacing as I'm starting to go through the toe. They're just general purpose trainers I suppose, the basic UA HOVR range and (I thought) they'd done well enough with 2yrs out of them, but now you have me thinking...
and @Orikoru last post hints at some previously 'untapped speed' advantage I might get too