Quote from dbphoenix:
Since trend channels are of course diagonal, the upper and lower limits will increase with the passage of time. The upper limit of the 4yr NQ channel, therefore, is currently around 3440+/-. Given that there will be errors in a 4yr-long line, small though they may be, those errors may amount to 20 or 30 points. Traders are therefore advised to be extremely cautious at these levels, particularly when it comes to further upside.
FYI, the mean for this current channel is around 3200. For the ES, it's around 1600.