Jobs that don't develop you — same work, same skills, no growth in scope or responsibility — are slow career death. Most people stay too long in stagnant roles because the day-to-day is comfortable. 18-24 months without development is the signal to start looking actively.
Signs of stagnation
No new challenges in 12+ months. Skills haven't grown. Same reports, same projects. Manager doesn't engage with your development. No clear path to next level. You could do this job in your sleep.
Where to look
Internal first: different team, different function, geographic move. Often easier than external and preserves benefits. External next: same level at company that will stretch you, or step up at company desperate for your specific skills.
The cost of staying
Skills atrophy. Network narrows. Salary lags market (internal raises typically below market rate). Identity tied to underwhelming role. Most stagnant-job stayers regret it in retrospect.