The invention of the printing press probably marks the beginning of the decline of civilization. Once you have it, science follows close behind. Next thing you know the idiots have better weaponry. Then atom bombs. Meantime, social organization becomes increasingly dependent on technology, which becomes increasingly vulnerable to error or sabotage. If we can judge by our own experience, it looks as if you get the printing press, then about a thousand years. After that it's back to the trees.