1. Freeze the set of features.
2. Continue to pay programmers to polish the software for several years while it is being actively used by many people.
3. Resist adding new features or updating the software to feel modern.
If you do that, your program will asymptomatically approach zero bug.Of course, your users will complain about missing features, how ugly and ancient your products look, and how they wished you were more like your buggy competitors.
And if your users are unhappy, then you probably lose the "used heavily by a lot of people" part that reveals the bugs.