Yeah, and there's no single golden rule. Everything would depend on: a) the bug b) the product There can also be cases where it's more expensive to find and

Yeah, and there's no single golden rule. Everything would depend on: a) the bug b) the product There can also be cases where it's more expensive to find and fix the bug as opposed to some customer finding a bug and reporting it. There's reasonable amount of testing you should do. You can never be sure that there aren't any bugs and at certain moment, proceeding tests wouldn't any longer be cost beneficial. A bug could be some button's focus border being of wrong color. No one notices this despite having spent 20 hours testing, running through the site in dev, and then one day designer happens to notice it and makes the report. Developer will have to change one line in CSS, they don't even have to deploy it immediately, but can deploy it together with everything else. Depending on the pipeline of course. In retrospect are you going to go ahead and conclude, that we should have done another 20 hours of testing to definitely spot that "bug" because it's 100x more expensive to fix it in production?