The husband, wife, and bull would have to be very good friends for a permanent live-in situation.
The slightest bit of jealousy will doom a relationship quickly. And may have unintended consequences.
It's a totally different dynamic compared to a weekend or even a week long visit.
A GF and I had this discussion at one time. It began as her fantasy of having a live-in lover in a very rural environment.
We thought of trying one week spent with her husband as they normally would, and the next week would be spent with her lover as his defacto wife. We're flexible enough to consider a two week on/off period, but any longer would be too long.
During her time with her lover, they are free to come and go and act as man and wife. Meals, evenings, or activities wouldn't necessarily be spent together with the husband.
Of course, this could mean the husband won't have the pleasure of watching or listening to them fuck or performing clean up, but if the end result is increased sexual fulfillment, it's worth it.