6 months Damien spent in Iris' soul space.
It wasn't 6 months spent exclusively on "physical" relations. It could be considered time spent to deepen their bond now that their feelings were clear.
But Damien couldn't spend all his time here, nor could Iris be distracted by him forever.
After all, her soul was still healing. She needed to focus on supporting its growth if she wanted to truly harness its potential when she returned to the real plane.
Iris' soul went through a qualitative change. Though it was the same soul, its form was so different that, to Iris, it felt like a completely new soul had been housed in her body.
It held power she had yet to comprehend, and her already monstrous talent would soon become absolutely incomprehensible.
To acclimate to it, she would need a year or two at the very least.
Damien opened his eyes in the real plane and smiled.