You are a SaaS and email marketing expert. Write a detailed, 2000-word blog post with 10 free trial extension re-engagement email templates. For each template, include: 1) Inactivity during trial, 2) Extension offer, 3) Subject line options, 4) Email body with offer, 5) Call-to-action buttons, 6) Personalization, 7) Metrics to track (trial reactivation), 8) A/B testing ideas, 9) Examples, 10) Conversion follow-up.