I think there are too many factors that influence healing which makes it impossible to say how long the process takes. Also I don't think there's suddenly a point where one says they are healed, and that's that. No more work to be done.
It's about 20 years since I was raped. Most of my 'healing' has been in the last 3-4 years. Before that, I was in denial. Denial about how badly I was coping, and denial about how much determined hard work I would have to put in to make any sort of difference to my life.
I also tried a great many therapists /psychologists / psychiatrists, until I found the 'right fit' for me.
Eventually, everything came together at once. Acceptance, learning what healing would involve, endless searching for the right sort of help, and eventually finding an amazing therapist who I 'clicked' with. Finding a psychiatrist who understood me, and together finding the right drug combination to stabilise me enough to begin intensive trauma therapy. My willingness to work hard and go to hell and back in therapy, a supportive family and stable home life.
It also remains a constant process. Learning to manage my PTSD. If I don't look after myself, PTSD symptoms will quickly bite me on the backside, particularly during times of stress. Healing for me is still a work in progress, but I'm 1000% better than I was 3 years ago.