If you dont look every day at the price, you will keep this investment at least 3 years and you dont need the money, then yes you should buy even at ATH today
Why ath, bitcoin is only increasing in viral value. The reason behind most the people are behind is because of its potential and price. For a past 6 months value moved more than 700$. These kind of achievement only btc to follow us on it.
Bitcoin prices increase almost per annual. When it touch $1000 it's bring us 200% from last year. If I know bitcoin from 2011, yes I should buy as much as I can buy and hold it with this knowledge about cryptocurrencies.
Unfortunately, beleive is the first rule on investment. And now peoples beleive in bitcoin is get strong day by day and make this a good way to invest your money.