I like variety, I like the excitement of meting a new woman every time. New set of tits, different faces, different style of blow jobs, different arses, pussies, etc. I do re-visit some prossies when I haven't had time to look for new ones but not as often that I would call them regulars.
Someone mentioned they need the emotional attachment that you build with regulars; I don't need that. I'm married, I have a lover/fuck buddy and I suppose they cater for my "emotional needs" to the opposite sex. The last thing I want is to get emotionally attached to a prossie. Strictly business for me.