I certainly hope you are joking about that last line.

A hard limit is a hard limit.
An unwanted gang bang is rape.

If in your fantasy, every slave eventually wants to experience or looks forward to this activity, then let's be clear that it is indeed a fantasy.

I'm wondering if you meant to put this thread into my BDSM life and not sexual fantasy.

To answer the original question for real life:
No, for me it's not important.
No, for my pet.
Yes, he's experienced them in the past.
No, he doesn't want to be shared in that way now.
Therefore, its something we can both do without.

For fantasies, reading, writing, and mental role play:

Whoo hoo! The thought can be quite arousing!