Is there a pattern of activating Pharah's thrusters that lets you stay in flight for longer? Both just the hovering and when combined with her Jump Jet.
Like Mage said in the comments, half second pulses are optimal because it allows pharah's fuel to refill without falling too fast due to gravity's acceleration. Maintaining somewhat of a constant, but still slightly decreasing, height.
It is also worthy to note that Pharah's fuel is refueling as long as she's not using it nor sliding/stuck on a non-standable surface.
This said, you don't have much room to stay in flight if you want to stay unpredictable. Just make sure to gain the most height possible by using your fuel and jump before using your first "Jump Jet".