It is important to stay connected with your colleagues even if they have moved on to different parts of your company or to other companies. You never know when you will be in a position to help a colleague or they will be able to give you career or business advice. It is much easier to have shared benefits if you have both stay connected. Now everyone is busy but if you set yourself a goal to stay in touch twice a year, once by email and once in person, there will be a continuity in the relationship. There will also be a sincere appreciation for your proactiveness and follow-through.