How long can it take to Heal Plantar Fasciitis?

I was diagnosed with this 8 months ago..and that was after suffering for about 3 months with it before going to the doctors. I had been faithfully walking the treadmill for at least an hour a day most days close to 1 .5. The doc said I was over stepping my stride? We'll I have the inserts in my shoes I bought sacounys 2 months ago (they feel better then the inserts) but even with stretching it still hurts..some times it will throb for several hours after stretching. The doc said it can take several months to heal...should this have healed by now? I have given up on running..Im not a athlete, I was just looking to get healthy. I tried the bike...it felt fine while riding it, but I was in pain for two days after. I am limping everywheres!!