It is recommended to regularly update and upgrade a custom web application to ensure optimal performance, security, and compatibility. Updates and upgrades address bugs, vulnerabilities, and outdated features, improve performance and user experience, and ensure compatibility with new technologies. The frequency of updates and upgrades depends on various factors, including the complexity and size of the application, security needs, industry standards, and user feedback. Generally, it is advisable to schedule updates and upgrades at least quarterly or semi-annually. However, critical security updates should be applied immediately. Working closely with a professional software development company can provide valuable insights and guidance in determining the appropriate update and upgrade frequency for your specific web application.