You have the ability to set the timing of the stages during the initial flight setup. The total duration can be anything from minutes to weeks. (Although, we typically recommend no longer than one week.)
The default split of time between the two stages is automatically split into 2/3 for Stage 1 and 1/3 for Stage 2. For example, a 1-hour flight will be 40 minutes in Stage 1, and 20 minutes in the Stage 2. Flight end date and time will also be listed here.
Once the flight is created, you cannot modify the timing. However, be on the lookout over the next few weeks, as this is subject to change :)