Yeah, you might as well not bother. There's no real choice there as it's not a risk of an encounter, it's a guarantee. It's a quantum ogre with extra steps. Just roll 1d8 for which hour of the rest the encounter happens. After the first encounter, roll your 1d8 again and if they're still resting after than many hours, they get a second encounter. Lather, rinse, repeat.
ETA: I just ran that through anydice. It's the equivalent to asking the players to flip 11 quarters and if any of them come up tails, they have an encounter. Not really what I'd call a fair ask.