A different question would be 'when does the next bubble happen'
I guess to sell i don't wait for new ATH but i wait for the next bubble.. and then just try to sell at a good point (this will be bad haha)
When saying 'bubble' i don't even have a definition,
i just think about a time where
it's going up for a longer time and fast
and people going cracy only posting trains and rocketship-pictures.
Well, I think that it's probably going to be at around 2020 when a lot of people are adopting bitcoin as their new primary online payment method. When there is adoption, the price will rise.
Next bubble? Perhaps next halving. No one can tell.