Rich Model vs God Class

I have a legacy code containing some behaviour classes, like services and controllers. My model is pretty anemic. It's just a repository of getters and setters, and I wanna refactor it. There is a thin line between Rich Model and God Class. I'm afraid to refactor my anemic model into a god class.

I wanna some opinion about how many lines is acceptable into a model class, and how many methods should I use without separating.

I know it's a unique perception from project to project, but i Wanna know some global opinions...

Thanks.