Pretty much every Domme I know does spitting in sessions when it is on your interest list... And the venn diagram of Dommes who do GS and spitting is probably a 99% overlap.

Can't say how most Dommes would feel about a whole hour of having to constantly hydrate themselves to expel fluids out of some hole in their body but just as an add-on activity while you are tied to a cross or on your backbon a bondage bed, is a pretty standard thing.

Is this a generic question or have you actually run across Dommes who have this on their limits list?