It's not like Lucifer sleeps much better. There's usually some part of him, physically or mentally or both, that is making contact with a pulse point. That if Istredd wakes up, he typically does too, that he might know Istredd's resting heart rate better than his own.

He might, eventually, work through that.

Maybe.

I would hope that does it for you considering I am a prick most of the time. If Istredd wasn't about that they were not going to last for very long, but then they've made it this long for being friends. Months? It really has been. So you did neither and instead just simmered on low heat.