It really depends on the approach. I like mothers yet, but still attractive. I don't mean the "seems too young to be a mom". But some milf actresses still have the milf charm, others not. There are even some milfs that I've liked when I was younger, but now they're starting to notice their age, even for a milf.
Basicly I liked the milfs that are were mothers of my friends at school, not from the university, if you get my idea. I like them because they're mothers and attractive, not because they're old. It's as if you see a teacher as attractive.
But anyway, I guess that's subjective after all, others probably a completly different view. Thanks for the answer though.