Hi TAS,
Not sure if I have said hi yet, so welcome!
It really does vary depending on the person, the severity of the abuse, how much support they recieved as a child, how much support they have now and how far and how deep they wish to go in their healing. That said, if the childhood trauma was long lasting, especially from a main caregiver, you usually measure therapy in years. That's not to say your life doesn't improve along the way, it's just that there are usually complex, very integrated behaviors that need to be addressed as well as needing to complete some developmental skills. To compound this, there are such intense trust issues (reasonably so mind you!), that it can take several years before enough trust is built with the T before really digging in (although the trust building and work tend to be woven together throughout the work.
I was sexually abused (as best I can piece together, I didn't remember until my early thirties) from the age of four until I was nine when my parents split up. My dad was also an alcoholic who then dissappeared. I have been in therapy for 26 years with two therapists. There have been breaks, sometimes of years, but therapy has been a part of my life for a long time. At this point, I really feel like I have healed from the trauma, but I continue to go both to deal with issues that crop up as I am living more fully and taking on challenges I would not have risked before and because I just value the depth of the relationship and continuing to grow (in other words, I seem to be one of those people who just never leave.
).
Sorry, I know it's frustrating not having a more definitive answer, but the truth is that it takes as long as it takes and only you can decide how long and how far you wish to go.
There's an entry on a therapist's blog that I like on time in therapy, I think you might find helpful:
Long term clients AG