We’re here to help!
I’m sensing we may have to go at this a few times and I want you to know that is NOT a problem. So, just be patient with me and keep asking your questions (and answering mine) so that we can get you the helpful answers you need and want, OK?
I want to double-check: You’ve been working with the PONR field, not the stack, is that correct? (I had gotten the idea that you had been working with the stack.)
This is important because you had told me that you felt “exhausted” from your PONR. If (because I don’t know) you had that effect after only 1 play of your PONR field, that’s important (to me). That tells me 2 things. The first is good news. It means that your 1 play of your PONR field is working (Yay!).
The PONR field is a comfortable field for most people. If you’re feeling exhaustion after a single play of the PONR field, I’m taking that as an indicator of your energy systems using the field to heal yourself. I think that’s good news.
And more good news is that your healing doesn’t have to be (too) uncomfortable for you. You can reduce your exhaustion by playing a portion of your field in a session. If I were in your situation, I would play 1/4 of the field in a session and see what that’s like for you. And I would only play that 1/4 one time a day. Then, I would slowly play a little bit more and more of your field until you can play the whole field without having your exhaustion. As you do your more of your healing, you’ll be more and more able to have a good experience with your field.
While you’re doing this healing, I would hold off on ALL other fields (with one exception, which I’ll get to in a minute) until you can play 1 full listen at 3 different times during your day without any exhaustion. You can (and this is my exception) play one of the free grounding fields (Release: Automated Grounding, Newly released: The Schuman Resonance, The Tree Experience seem to be the most popular ones) after your listen to your portion of your PONR. And if you can do physical grounding, I’d recommend that you do that as well.
So, to recap: a comfortable portion of your PONR field and a grounding field and that’s it, until you’re no longer exhausted. Make sure you’re drinking a lot of water (helps you integrate the field as well as helps your healing), getting some re-energizing exercise (don’t kill yourself), eating good healthy food and getting a healthy amount of sleep.
That’s what I would do. When you can listen to your PONR for 1 full play, 3 times a day, without your exhaustion, then we can talk about what other fields you can add.
The simple (and accurate) answer is until you no longer need it. That is until you can take a break from listening to PONR and still maintain your strong mindset (whatever that means to you) without your PONR. Everyone’s going to be different, not only because we’re different people but because we have different types and amounts of stuff to heal. When you’ve been down in the last years, it wouldn’t be uncommon for you to need to use PONR for a month or more. (That’s still way, way shorter than most forms of therapy.)
Use that time to get really clear on what a “strong mindset” means to you. How will you know when you have your strong mindset? When you’re clear on that, then you’ll recognize when you accomplish it.
No, not directly. This field will help you heal your down-ness, hopelessness and depression that you were talking about.
When you do your healing and you gain your strong mindset, that will help you absorb better more fields. (But do you want more fields? I mean, haven’t you been asking–many times in many places–how you can eliminate fields? So, I’m confused. 
)