[The incredulity does shine through, though it's hard to string a sentence from it. Still, it reads as doubt, and Connor clarifies.]

We really don't get tired. We don't feel pain, and though we can be injured, it's easy enough to work through it if need be. For as long as necessary.

[Parts can be worn out, grow sluggish, core battery life can technically go dead after a full century or so. But tiredness is not something androids experience.]

You worry often, don't you? That must be part and parcel of being a medical unit.