It happens and did happen a few times but by the time a bull finds out where we live we already know him and trust him. We did have the occassional guest over we hadn't properly vetted for convenience sake but it was rare.
There was two or three younger ******* she had a fascination with and invited over. My wife liked very young guys she could train and teach them but also she knew younger single males had a lot of free time and like to hang out and party. So this meant they would be more likely to not have anywhere to go and might be more likely to just come over and hang out if they felt welcome and we entertained them. They could also recover quicker and have several sessions a visit.
So they would occassionally come over unannounced but it never was too bad of an issue with a couple of exceptions where family was visiting or she was hosting a seminar with her girlfriends.
Those times when they showed up we told them they were the lawn mower *******. We invited them in, she said to follow her upstairs so she could write them a check and would then take him into our bedroom and did what he wanted, quickly and walked him out. She blew one of them and swallowed most of his cum and rubbed the rest over her face and then went back down to her seminar and hugged and kissed her friends on the cheek when they left and also got a few cheek kisses. You could smell the cum when you were close to her it was so fresh.
The other time, when my family was visiting she took him upstairs, told him to make it quick, turned on the radio, told him to lift her dress, sucked him for a bit then let him pound her pussy while insisting he verbally humiliate me while hes pounding her. Then she walked him out and sent him on his way.
Othertimes, when we had unannounced visits if it were late at night she would just go ahead and bring them into our bedroom and see if they wanted to just spend the night since we were already in bed, I would just scoot over to make room for him and she would spread her legs and let him take her pussy right away so we could get some rest.
If it were earlier she would just let them hang out in the living room and watch tv with me while she set beside them and sucked their dicks or leaned up against the chair and let them take her pussy there. Then they could either leave or just hang out for a bit. or stay for another session.