You are an email marketing analytics expert. Write a detailed, 2400-word guide on next purchase prediction. The guide must cover: 1) What is next purchase prediction, 2) Building prediction models, 3) Identifying customers likely to purchase, 4) Triggering emails based on predictions, 5) Personalizing offers, 6) A/B testing predictive emails, 7) Measuring lift in revenue, 8) Tools for prediction, 9) Examples of next purchase emails, 10) Continuous model improvement.