When should I stop beta testing?
So, when to stop testing? Simple: when you fixed all Critical and Major defects. There are both software development and client relation reasons not to make the new version of your product more unstable than the previous one. Resolving all defects of the two highest severity types gives you that.
What is a beta tag?
They are markers that designate new features available in beta either openly or to a closed group of users for testing and feedback.