3 years.

I've met with 13 therapists for more than 4 sessions (4 sessions is what I use as a benchmark to say, "I gave this a good try.") Until my current therapist, I'd met with all of them for less than a year each.

7 of the 13 caused more harm than help.
Totaling all the harmful therapists makes a rough total of 19 months.

Up until my current therapist, I'd had 4 helpful therapists. The helpful therapist time totaled 9 months.

I spent way more time with harmful therapists than helpful therapists.

Now I meet with my current therapist, who is really, really helpful. I've been seeing him for 3 years, and (bless him!) he tipped the scale so I've now spent more time with helpful therapists than harmful.