Familiar slippery hole vs strange ass
There's a wide range of emotional involvement in sd / sb relationships. Nando seems to be in love, Snake27 had a funeral for his sb's cell phone when she left him, Golf has long term (monogamous?) relationships but manages to avoid emotional involvement.
I use to fear I'd get romantically involved if I really enjoyed fucking a particular sb, because fucking and romance were always in some mysterious way hard wired to each other in my system. Now I don't think I will. I instinctively start to withdraw from an sb emotionally after a few trips up her vag canal. I worry the girl will get attached, dependent, expectant, whatever. It means the fucking becomes less satisfying but I really don't desire the romance because it would mess me up.
At the other end of the spectrum was a monger on another thread who said all sbs were just pigs wallowing in filth (or some such shit). This is an extreme variation of the "all sbs are working girls" mantra, which is more of a moral judgment than it is descriptive of behavior. I think this belief helps prevent involvement for some.