I could offer a different data point, but since it's all subjective experience anyway, just make your own call. I've enjoyed long-term therapy because I found more things I wanted to work on. Ironically, it is my therapist who reviews things on a regular schedule and asks, "why are you coming to therapy now?"
(If your therapist isn't doing that, maybe that's a red flag that you are being taken advantage of?)
It may also indicate you really need the therapy. That's the conundrum.
You need sometimes assess (reflect), possibly with your therapist, how they are aiding you effectively. In The Netherlands, there are waiting lists for psychiatrists (and a shortage), as well as waiting lists for specialized psychologists; hence they get paid either way. They'd rather have a client who benefits from their therapy.
It's less about fixing things that are profoundly broken and more about incrementally trying to make the most of the brain you're given.
It's like asking, "what does a junior engineer get out of being mentored by a senior engineer that they couldn't just figure out by coding or reading blogs?" A therapist brings things like context, breadth of knowledge, and honesty. I felt like the therapist wasn't incentivized to sugar coat things to spare my feelings, something close friends and family might do.
I am not sure about seeing one for 5 years, though. The point of a therapist is to make themselves unnecessary, in my opinion - they're supposed to give you the tools needed to do exactly what you're saying people should do - understand their behavior and change it.