Next sell signal will be when 3 day RSI is over 90 to 92.
I tend to think that above 85 RSI proved to be a tradable signal. But perhaps you only look for the absolute peak in the next bull run?
Depends on your risk tolerance. During the December 2017 parabolic top selling at 3 day RSI of 92 would have got you out at about $16500. Then you had another chance to sell over $16000 on the dead cat bounce in January 2018. Back then the public (even some seasoned traders) were not even thinking about selling, expecting the bull run to continue. Then there was money to be make shorting all the way down to $3122. If you used 3D RSI under 18 you would have closed your short at about $3500 - $4000.