"... Why would it?" Duke is honestly confused by that. "I would need to... consecutively cast the spell some hundred times or more to reach exhaustion. It would be a moment of focus from me, and then perhaps half a minute, if not far less, to regain the energy used in healing you." It takes far less.

"The worst I would get from using magic is exhaustion, unless it was something offensive and then there are a variety of elements and potential hazards there."