People giving up hope is a sign of reaching the bottom, slowly but surely. My own indicator is not looking at the forum for weeks. That's still some time away.
Fun indicator - personally I'm checking here once a day maybe three days a week instead of multiple times every day. The last time I was at that point was during the summer of 2013, which was also super boring.
Then we'll know we're at the bottom when bitcointalk only gets 5 posts a day.