I've never been to a therapist for anything that can be described as a diagnosable condition, but I have spoken to one about stress management and things of that ilk. For "amusement" I discussed similar things with an LLM.

At a surface level, the LLM was far more accessible. I didn't have to schedule an appointment weeks in advance. Even with the free tier, I didn't have to worry about time limits per se. There were limits, to be sure, but I could easily think about a question or the LLM's response before responding. In my case, what mattered was turnaround time on my terms rather than an in depth discussion. There was also less concern about being judged, both by another human and in a way that could get back to my employer because, yeah, it was employment related stress and the only way I could afford human service was through insurance offered by my employer. While there are significant privacy concerns with LLM's as they stand today, you don't have that direct relationship between who is offering it and the people in your life.

On a deeper level, I simply felt the advice was presented in a more useful form. The human discussions were framed by exercises to be completed between sessions. While the exercises were useful, the feedback was far from immediate and the purpose of the exercises is best described as a delaying tactic: it provided a framework for deeper thought between discussions because discussions were confined to times that were available to both parties. LLMs are more flexible. They are always available. Rather than dealing with big exercises to delay the conversation by a couple of weeks, they can be bite sized exercises to enable the next step. On top of that, LLMs allow for an expanded scope of discussion. Remember, I'm talking about workplace stress in my particular case. An LLM doesn't care whether you are talking about how you personally handle stress, or about how you manage a workplace in order to reduce stress for yourself and others.

Now I'm not going to pretend that this sort of arrangement is useful in all cases. I certainly wouldn't trust it for a psychological or medical diagnosis, and I would trust it even less for prescribed medications. On the other hand, people who cannot afford access to traditional professional services are likely better served by LLMs. After all, there are plenty of people who will offer advice. Those people range from well meaning friends who may lack the scope to offer valid advice, to snake-oil salesmen who could care less about outcomes as long as it contributes to their bottom line. Now I'm not going to pretend that LLMs care about me. On the other hand, they don't care about squeezing me for everything I have either. While the former will never change, I'll admit that the latter may. But I don't foresee that in the immediate future since I suspect the vendors of these models won't push for it until they have established their role in the market place.

Why do you think the lack of time limits is an advantage?

There is an amount of time spent gazing into your navel which is helpful. Less or more than that can be harmful.

You can absolutely make yourself mentally ill just by spending too much time worrying about how mentally ill you are.

And it's clear that there are a rather large number of people making themselves mentally ill using OpenAI's products right now.

Oh, and, aside, nothing stops OpenAI from giving or selling your chat transcripts to your employer. :P In fact, if your employer sues them they'll very likely be obligated to hand them over and you may have no standing to resist it.