Stopping a testing phase (Or) when to stop testing the application are determined with various aspects. A product is built and enhanced based on the customer's needs and requirements. So the software companies encourage their customers to provide a valuable feedback about their software and there are few customer who provide the honest review about the software and if that review contents any new idea/ suggestion or requirement, based on the business use case the product management team member will take call whether or not to include the new idea or product behavior change.
If the PM (Product Management) team decided to include the idea given by their customers then that ideas are developed and implemented in software and before releasing the update to market, the new ideas are sent for the end to end testing process and in this testing phase the QA Testers are suppose to perform an intense test and find as many as bugs possible to ensure that this bugs are addressed before releasing the update to market. In this phase although the end to end testing is put on pause, however if the customer revert stating that, the found few issues/ error then the testing process is reinstated to ensure that those issues/error are addressed by the concern team members.