twenty-eight years and a million words
So, it looks like a supernova could have stripped the Earth of its ozone layer 360 million years ago, at the end of the Devonian. This was just when some creatures were beginning to live on the Earth's land surfaces, and it took 40 million years to recover. 200 million years after that there was the Chicxulub impact event. Space is a pretty rough neighborhood.
If I had my life to live over, I'd try to make more mistakes next time. I would relax, I would limber up, I would be crazier than I've been on this trip. I know very few things I'd take seriously any more. I'd certainly be less hygenic... I would take more chances, I would take more trips, I would scale more mountains, I would swim more rivers, and I would watch more sunsets. I would eat more ice cream and fewer beans. I would have more actual troubles and fewer imaginary ones. Oh, I've had my moments, and if I had to do it all over again, I'd have many more of them, in fact I'd try not to have anything else, just moments, one after another, instead of living so many years ahead of my day. If I had it to do all over again, I'd travel lighter, much lighter than I have. I would start barefoot earlier in the spring, and I'd stay that way later in the fall. And I would ride more merry-go-rounds, and catch more gold rings, and greet more people and pick more flowers and dance more often. If I had it to do all over again - but you see, I don't.