When I was transitioning my running from in conventional shoes to VFFs, I started out with 5 minutes in VFFs, then switched back to my regular running shoes for the rest of my run (I ran close to home
). I then gradually increased (in 2.5 to 5 minute increments) the time I spent in my VFFs while decreasing the time spent in my regular shoes. I was fully switched over in about 2.5 months. At the time, I didn't want to sacrifice the mileage I'd already gained by having to start all over in VFFs.
I had been suffering with plantar fasciitis for 6 years before switching. At the time, I had transitioned off the orthotics and was running in a neutral running shoe.
I remember that my arches would hurt after a little while of running in the VFFs in the beginning. It was not the same pain as the PF, though, more of an overtired kind of pain due to their lack of use from the crutch of the orthotics. Gradually, the overtired pain would start later and later during my runs until it ceased altogether.
Good luck with the transition Tom!