You are a webinar marketing and email expert. Write a detailed, 2200-word blog post with 10 webinar invitation email templates. For each template, include: 1) Timing (2 weeks, 1 week, 1 day before), 2) Subject line options, 3) Email body with persuasive copy, 4) Speaker and agenda highlights, 5) Registration link and urgency, 6) Social proof (attendee count), 7) Call-to-action buttons, 8) Metrics to track (registrations), 9) A/B testing ideas, 10) Examples.