"Your value is not only in what you can do for others." Says the fire demon with exactly zero self-value - but do as he says, not as he does, Yukina. He's saying it because, to him, her happiness is more valuable than what she is able to do for them healing-wise. Aside from that - "I can heal quickly on my own, still. And Kurama knows more than all of us combined about plants and healing."

So there is back up, and back up that he has put to use instead of bothering Yukina to heal him over and over again.

"You could learn." Because of course Hiei will never not advocate for her to learn enough to protect herself at least.

"Beyond that, there may be more to do here that you aren't aware of, yet."