We can compare Bitcoin over the past year or two to Gold from the birth of Gold futures contracts to see why Bitcoin has a good chance of hitting 44k by year end or by early 2019.
When each asset broke its previous ATH it pushed for a new ATH well above the first (peak Euohoria zones, Gold 4x and BTC 20x).
Each asset topped out at 1.0, then retraced 0.382, tested 0.786 and fell.
Gold bottomed out at a previous resistance zone similar to BTCUSD at about $5000.
The Gold 'flat' market from 1980-2006 will likely be a much shorter process for BTC. The Gold catalyst was the movement of capital to safehavens after the financial crisis, we could see similar behaviour towards BTC in the future.
BTC's first Euphoria zone has five times greater return's than Gold's peak euphoria zone, later Gold hit the 2.618 level. If Bitcoin mimics Gold and hits the 2.618 level at 44k. By this analysis, 44k seems like a CONSERVATIVE long term estimate, considering bitcoin's volatility and previous price appreciation.