I have read these posts with much interest. I am not experiencing frugal fatigue, and right now it doesn't feel like I ever will, because the changes I have made are not requiring any willpower to sustain. I don't feel deprived at all. As a matter of fact, I feel liberated.
BUT, I have always had a "gluttony" mindset, so I'm not sure where this is going to lead. And I don't think this is just a product of being raised in consumerist America. I think it's a personality trait that has been part of me as long as I can remember, likely since birth. If something is good, I want more of it. There was no "optimal" amount for me; more was always better than less. My sister and I joke about this, because our approaches to life are entirely different. For her, there is an optimal amount of everything (kids, work, pets, friends, free time, stuff, etc.) and her energy goes into finding that amount and protecting it. All of my energy goes into managing this "full to overflowing" life I have built, and when i have the tiniest bit of energy left over, I find myself wanting to add something new (to adopt another child, rescue more dogs, go back to school for a second Ph.D., to teach a night class in addition to working full time, etc.). Note, while these are not typical consumerism activities, they do all require additional resources.
I even find I have a strange thing with vacations. I get this sinking feeling as soon as it starts, because once it starts, it will soon be over, and I hate that feeling. As the vacation progresses, I find myself calculating ratios each day of how much has passed to how much is left. It's quite the opposite of living in the present, this constant calculation of past to future.
I think Mustachianism appeals to me, because I can see my gluttonous approach to life (even if supported by an underlying personality trait) is not serving me well. It is leaving me exhausted and dissatisfied. Mustachianism is really not about money for me, but about figuring out what's really important and letting go of as much of the rest as I can. I have not mismanaged money so much as I have mismanaged energy. It'll be really interesting to see what happens to my energy over time, and whether I become more energized or fatigued.