"11-17-15: Inna
Zd542, good cables , they can change dramaticaly for the better after 100-200 hours. I consider cables components."
I agree with you on that. Some cables take even longer than 200 hours to break in. The OP was asking about a phono cart for break in.
"11-17-15: Stringreen
To me hours are meaningless. Just listen and enjoy your music. If while listening something is bothering you, experiment with VTF, arm height, loading....it should be a quest for satisfaction and your ability to squeeze your system to provide it."
That's good advice, but with new carts, you need to be careful. A brand new phono cart can sound so bad you'll think its defective. For the first 15-20 hours, I can actually hear a difference with each new record I play.