If you sleep for 6 hours, when you return to consciousness your observations of existence are entirely consistent with the sort of observations you would have made had you been conscious of those six hours. Clocks have changed to indicate the passage of six hours. New posts and news stories, time-stamped to the missing six hours, will have appeared on the websites you frequent. The sun will have changed its position in the sky by the amount you would have expected it to in six hours. The programmes on TV would have changed to what was scheduled to have been on six hours after you went to sleep. The clothes you left to dry would have dried as much as they would have in six hours of constantly checking them. I could go on ad infinitum, but this all adds up to fairly good evidence that the world continues to exist in much the same way when we aren't conscious of it.
It is taken on faith that these things happened as we did not experience them, and on faith that we suffered a period of "unawareness". Do you know for certain that your awareness ceased?
My point is that we can experience our awareness, but we cannot experience our unawareness; therefore, any episode of awareness will be more evidenced than an episode of unawareness, making awareness the more evidenced state. What is more, we are never aware of experiencing unawareness, but are always aware of experiencing awareness.
Thus, as far as I am aware my awareness is eternal, for whenever I could be aware of my awareness, my awareness was present, but there were no times when I could be aware of my unawareness that I was aware of not being aware.
The only thing of which one can be certain is that which one experiences for one's self.
Jon
"Can we say the chair on the cat, for example? Or the basket in the person? No, we can't..." - Harriet J. Ottenheimer
"Dim bulbs save on energy..." - jar