Onyx looked at Tarentek, thankful for his calm statement helping her to find a thread to follow in her confusion. He's right, along with the potential of an uprising not too long from now, and the approach of the empire, Onyx also wouldn't be in the nest for a while after Tarentek gets better, because as soon as he is well enough they would be leaving for the Tel Nof mission. Anytime past that point, when she and Tarentek would have to leave, might as well be considered too late. 

"I think sooner would be better too. Would the day after tomorrow bee soon enough, but not too soon?" Onyx asked her father. Raldel didn't seem surprised by her answer, and he responded quickly, saying that then would be the perfect time. These rituals rarely are announced much sooner than a day or two before anyway.