stay in touch
1. To maintain contact with another person, especially at intervals so as to remain up to date with each other's lives. My old high school friends and I tried staying in touch after we graduated, but we all started drifting apart once college got underway. Now, make sure you stay in touch, OK? I want to hear all about your time in Paris!
2. An informal parting phrase, used especially with a person one isn't likely to see again anytime soon. OK, Deborah, thank you for your audition. Stay in touch! It was so good to see you again, cousin Jeb—stay in touch!