Once a company has PMF, Reforge's framework (cited by Casey Winters) splits ongoing product work into four categories: Features (incremental additions to the core product), Growth (optimizing acquisition/activation/retention loops within the existing product), Scaling (operational and infrastructure work to support more volume of the same thing), and Expansion (building something genuinely new that extends what the company does). Expansion is the hardest and riskiest category, and is the subject of Five Types of Product Expansion (Easiest to Hardest) and A Second Product Only Needs to Fix One Weak Link. Companies often over-invest in Growth and Scaling while avoiding Expansion because it's a distinct discipline requiring its own timing model — see S-Curve Evaluation (Next Growth Wave vs. Enhancer).