Will close #504

This principle focuses on the active maintenance and regular updating of systems over time, ensuring they stay modern, secure, and efficient. While principles like "Write maintainable, reusable, and evolutionary code" emphasise how to build software that is easy to modify, and "Well managed code" highlights best practices for managing code collaboratively and effectively, this principle addresses a different phase: the ongoing responsibility to actually apply those modifications by updating codebases, dependencies, pipelines, and infrastructure regularly.
The key distinction is that even the most maintainable code will eventually become outdated if left untouched. This principle ensures we avoid the trap of stagnation, where multiple skipped updates result in systems that are hard to upgrade or replace.
By focusing on the watching and maintaining phase, this principle highlights the practical steps needed to prevent technical debt, security vulnerabilities, and costly big bang upgrades. It complements existing principles by reinforcing the idea that great systems don’t just need to be well-designed, they need to be actively cared for over time.

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