Minimum Cock Size to be a bull??

That is really subjective. Many wives don't want larger sizes. I'm a size queen and Mr HW is 8 inches, so I prefer 8 or larger and thick is great. The ability to STAY HARD is so important though. So many guys can't get or keep it up. I have had lots of fun with 6 inch guys who are enthusiastic though as well. They just don't hit those extra special places for me that I enjoy. As for "long lasting", I'm different in that respect. I prefer a guy who can cum pretty quickly and multiple times. I prefer guys who are DDF and will play bare, but far more in demand in the lifetyle are guys who play with a condom and have no problem keeping it up while wearing one. That's just not my thing though.

Mrs Hotwife
Have never had a problem being able stay fully able to perform till everyone is completely satisfied. I can even cum multiple times and keep going.