Hi,
I had a similar experience and in our case we were going to add Product Categories so after spending so much effort in the creating the Product categories (unlike importing historical data this had to be created so you can imagine the frustration) and then loading was a slow process, but having asked this question about the limit if any and not getting a response before or after loading and facing the issue where the Product Category Work Center did not load the data.
So basically it was hitting against a dead wall and had to start from the scratch and re-plan the whole use case.
Regards