Not forever. In 20 years that $40K will lose half of its purchasing power. Plus unless you can magically guarantee 4% returns a year, you will be getting less and less out every year.
No mortgage, no marriage, no restaurants, no fancy gadgets, just a nice relaxing low cost of living life with friends who feel the same way.
Every once in a while I take some controlled investing risks, but hell if I would ever plunk 300k in a mutual fund and just safely assume everything will be fine when I check it 30 years from now.