How long can these ATH'S last before we hit another bear market.
Nobody knows. If there's one person who can give hint then for me that would be Charlie Lee. He has given a good opinion on the last ATH in 2017 and how it lasted in 2018. He said that if they can't the bears for long then they should start to sell, something like that.Anyone still buying at these high costs? lol 
Yes and it's just getting started.