I just got off the phone with the dealership...
I have developed the cam phaser rattle in the last month or so. I have a road trip coming up in a few weeks and given that sometimes this job takes a while, I wanted to make sure it was ok for me to go on my road trip before having it fixed.
Two things he said:
1) I will 100% not do any damage to my engine by continuing to drive without addressing the rattle. Once the rattle stops (so, 2 seconds after start-up) the issue that causes the rattle has corrected itself and the engine is running normally. So no damage to the engine.
2) They have parts readily available and the "cam phaser job" takes a week.
All of that, to me, was great news. Oh, and they always do a full oil change following the cam phaser job to make sure all is well there.