Reminds me of one of my favorite jokes.<p>The professor is lecturing, and says, &quot;The Sun will grow to be a red giant, destroying all life on Earth in about a billion years....&quot;<p>A distracted student suddenly sits up and cries out, &quot;Oh my god!&quot;<p>The professor says, &quot;What&#x27;s wrong? A billion years is a long time, you know. Nothing to worry about.&quot;<p>The student is visibly relief. &quot;Oh, great! I thought you said a million years!&quot;<p>Personally, I&#x27;d say a few hundred years is probably the reasonable max, maybe a thousand years. Beyond that, technology will be so incomprehensibly different that the risks and challenges will be completely different as well. What would be a civilization-killing asteroid today might just be &quot;ooh, tasty resources already on a convenient trajectory&quot; tomorrow. Or &quot;aw shucks, it&#x27;s going to make a big splash in the gray goo.&quot;