Dr. John Gottman recommends several strategies for maintaining passion and intimacy in a long-term relationship. These include prioritizing emotional connection, cultivating fondness and admiration for your partner, engaging in regular and meaningful communication, being physically affectionate, showing appreciation and gratitude, and making time for shared activities and experiences. Additionally, Dr. Gottman suggests embracing flexibility and compromise, managing conflict constructively, and continually learning and growing together as a couple.