Eurocity train: luggage limits and frequency

Hi, We're taking the train between Brussels - Rotterdam - Amsterdam, likely an Eurocity. I'm wondering if there's a limit on luggage (number of suitcases and size). Another question: on the Rotterdam -> Brussels route, it seems there aren't any trains on Saturday afternoons. Do trains run frequently on Saturdays and maybe Sundays in the Netherlands? Thanks in advance for your replies! :)

"I get the feeling there’s no service on Saturday afternoons. Do trains run often on Saturdays and maybe Sundays in the Netherlands?"

That’s true for this Saturday, May 24th. But next weekend, no worries—the trains should be running normally.