I wouldn't want to rely on being able to go back to work, or (even worse) my ability to both be cognizant the portfolio is in trouble early and admit it, but is something to have in mind.
This is a subtle point. I think generally we kid ourselves about how we will diagnose failure early, and move to correct it either by going back to work or other means.
Irresponsible is a strong word, and it applies more to ethics and morals than to anything else. If all that is being risked are an individual's or couple's well being, so be it, adults are allowed to go mountain climbing, etc, etc. which to me appears to be a whole lot more risky than retiring even very early.
So irresponsible? Who knows. Risky? Almost certainly yes.
When a human strongly wants some behavior, and wants to at least to pretend to being rational about it, he will very often allow only a truncated set of possible future states. Then he can reason, feel good that he did his due diligence, and still be guaranteed of having his desired action approved. This however may not have a lot to due with how well it works out over time.
The other thing I am not so sure about is this idea that if you don't crap out early, you are OK. I'm approaching 30 years, and it still seems to me that a number of very negative events could make my continue pleasant retirement a question mark at best.
I do think that a reasonably well financed retiree's life has more risk from his body giving out than his portfolio, but not I'm not sure. We all will die, whereas it is likely that very many of us will not run low on money. It does seem that most of us have likely heard of more relatively young people who came down with heavy duty illnesses, than formerly retired people who had to go try to find a paycheck.
Ha