This is a man conversation. What about girth?
I think men like seeing their wife / GF take a long AND thick cock. I think that if a guy knows how to use what he has, he can be only 8" long and be just as good/better than a guy with 12". Smaller guys are easier to suck, though. If a guy is too thick to get in your mouth, it makes it hard to give him a really good blow job. Yet, if he is too thin, then you can't feel him much during intercourse.
One of our neighbor's friends is thick as hell and about 9-10". He doesn't like to warm you up. He just likes to shove it in. Although I have come to enjoy anal, this one guy hurts. He shoves it in fast and very deep. And he thrusts so fast that there is so much friction that it feels like my butt is on fire. That is not a good feeling.
Another guy is just as thick, and because he takes his time, I can take him anally. And he feels really good. Men who have more experience, and actually care if the woman enjoys the sex, can work with a huge cock, and the woman is going to love it. A guy with a huge cock that is careless, selfish and doesn't care about the woman, he is not going to feel good, or be wanted back.
For vaginal intercourse, I think around 9" is about right. I know I can take it, and I know I can take all of it. When a guy is too long, he can't get it all in. And that is not only a waste, but it makes me feel inadequate when I can't take it all.
I don't think a guy can be too thick. It may take a while to be able to take him, but once he is in, YES! And if he is 8-10" long, that's a bonus. And if he really knows how to use what he has, all the better.