Phenomenal question! We ran a live-show at our local convention and over the course of the three hours the players used a facet 1 to 2 times each.
So, theoretically, depending on the amount of non-rolling roleplay the players do versus more roll-heavy content (especially combat) you could argue about 2 hours per facet.
Of course, if you want the game to be shorter (2 hours or less) don't hesitate to give them just one facet. After all, they WERE separated from the one who brought them to life in the first place. It would make sense that there's only a little bit of that original magic left.
Have fun! Let us know how it goes! Thanks so much for choosing our submission that means a ton!

