Long distance relationships, is all about trusting each other.
There are many different ways of knowing your relationship is lasting and that its going to be strong.
Its important to remember that there are different time zones and that one of you might be in front or even behind. But between the two of you, you work out a time that suits both of you to Skype ,face-time. But talking throughout the day is important, talking about your day.
planning trips to visit each other. Surprise each other, by going over to see them and surprise them. Its important to keep the spark alive, and take it in turn to go to each other.