My rant now...........I saw my son on Saturday, it was great being with him, but I cried loads after we parted as it will be two weeks before we meet again.
There may be a way to change that dynamic slightly.
Thinking back to your son's age...... I have many memories but most things tend to blend together. However the special days stand out crystal clear. The memories are as clear as can be, they make me smile. There was the event but looking back as a mature man, you remember the experience as a special gift, be it the words of encouragement, the love, the sacrifices that person made because when we grow up we come to really understand how kind and generous that friend or parent was.
Your every two week visit is an opportunity for you to accomplish in one afternoon or day what can't really be accomplished on an every day basis....... to make each of these distinct days as memorable as possible. To share a precious gift that will be with him for the rest of his life and yours.
Something experienced by both of you in the same place at the same time. Be it a movie, a favorite restaurant, shopping together, a sport. Meeting mutual friends if possible, visiting a museum, a concert, buying a book or DVD. Visiting second hand shops and 'lucking out' when you and your son find just the right fishing pole or musical instrument, or garment.
It's there for you guys to share. And when the visit ends the tears will be tears of joy.
In later years when your talking about this or that...... one of you will say......."remember that time we........"
And those will be the sweetest words to hear.