Patricia Aas discusses strategies for designing secure systems that can be easily updated and maintained over time. She recommends: 1) Ensuring code is version controlled and build/deployment processes are automated so fixes can be easily rolled out. 2) Limiting dependencies and maintaining control over the full stack to prevent issues caused by abandoned third-party components. 3) Documenting systems sufficiently so institutional knowledge is retained if the original team leaves. 4) Focusing on preventative security practices like input sanitization and encryption to reduce risk of vulnerabilities emerging over the long run.