Benzodiazepines like klonopin can be used long-term if you're willing to deal with a bit of tolerance. If you keep upping your dose at the first sign of tolerance, it's going to get way out of hand and isn't very sustainable.
It's not really IDEAL to stay on benzos indefinitely if you can help it. They are more useful to help you be functional while you work on your problems to hopefully find a better long-term solution. There is nothing technically limiting a person from taking them forever, but I wouldn't recommend planning on it, I would instead recommend using more suitable long-term meds and/or therapy to hopefully get you off of them someday. If I was a doctor, outside of a few rare special cases, I would make the patient demonstrate to at least keep TRYING to find a better, more permanent long-term solution by continuing to go to therapy or something, in order to get a benzo prescription.
And most doctors don't feel too differently. Most of them do NOT intend for their patients to be on benzos forever, and that's the real issue regarding whether or not you can take benzos indefinitely. There's a very good chance that at some point down the line, they will want to start weaning you off.
As far as when do your meds get increased... same deal. There's no real way set in stone to do it, and some doctors will tolerate a few dose increases, but the benefits of upping the dose will quickly be lost by increased tolerance, requiring you to up your dose again to get back to where you were, which increases your tolerance again to pretty much where you were before, and basically it's often bound to create a vicious cycle where the only thing stopping you from constantly increasing your dose if the doctor refusing to let you. You're NOT getting much more if any extra benefit for very long by increasing the dose, and the pointless tradeoff is that at these higher doses it will create a much more severe and dangerous dependence. So most doctors (and I tend to agree with this), if at all willing, will at most allow you to find a dose that works well for you EARLY ON, and then seriously discourage and generally not even permit further dose increases. You HAVE to be okay with the idea of the drug becoming a bit less effective over time because otherwise your doses will never stop increasing, and trust me, that's something you want to avoid, NOT to look forward to.