It's a good, valid subject to bring up. I'm 42, and my mom is 70. She has lupus and diabetes, so her life expectancy is probably about 80. After she passes away, I'm going to sit down and take a hard look at my finances.
I currently work in the public sector and have a definied pension available when I'm 65. With what I have in my IRAs and the inheritance from my mom, it might be possible to retire in my early 50s. If that's possible, I'd like to spend about a decade as a bike nomad before I settle into a more comfortable permanent retirement.
I've always had a strong sense of wonderlust, so I think I'd really enjoy spending 50s as a vagabond. In my 60s, I think I'll be too old, and would prefer to a more comfortable (but modest) retirement.
At this point it's all just dreaming, though...