Analyzing your code is cheap but valuable. Scouring your code and producing interesting metrics helps you keep check on all kinds of creeping issues.
Static code analysis, style checkers, cyclomatic complexity, code coverage and scanning for FIXMEs and TODOs are all examples of metrics that help you keep a watchful eye on codebase evolution. Adding thresholds to these measures as part of your verification protects it from corruption.
Monitor improvements but don’t waste time reaching arbitrary targets.