First of all, keeping in mind that attitude determines altitude, your approach that you're doing your time in hell until you are lifted up and exalted among the stars may not be the most productive one. "Embrace the suck" speaks more to attitude and it's not a positive one. If you're not happy where you are, do something else. If you don't feel it's economically beneficial, or if it's unsafe, or if it's unsavory, go do something else. Life is too short to be that unhappy.

How long do you stay there? Until you either decide to do something else, or until you get hired elsewhere.

There's nothing wrong with flying for a regional, except perhaps the pay, and in some cases the schedule. Some, as you've noted, are better than others. I've known pilots who spent most of their careers at regional carriers. They had their reason. The mentality that someone who doesn't go to a major airline has something wrong with them is a poor attitude, and smacks of ignorance. Not everyone wants to fly for a major. I know people who have done fire, law enforcement, crop dusting, corporate, instructing, and other things for their entire career, and who have been quite happy with their work and their life. Rather than worrying about what the captain who's been there five or six years is doing, worry about yourself, and let them lead their own life.

You're making the progress along the lines you've chosen. You're working on a career, working on a degree, and not at a point where you need to focus on how much time you've spend on the line yet. If you're still flying as an FO, you need to focus on upgrading first, getting PIC experience, and while doing that, on making applications elsewhere if it's what you wish to do.