Making true, lifelong friends is like planting seeds. People you meet and stay in touch with for the next 20 years will undoubtedly by wonderful friends in time, but people you meet today will not be the same as people you have known for 20 years. Living next to someone I have known for the majority of my life(assuming we are still very close) is very different than living next to someone I have known for 6 months. I understand the idea is that you still live near friends but it is just not the same.
I draw a different conclusion from your analogy though. One should continue to plant those seeds of friendship wherever you are. Friendship is not zero sum.
"The best time to plant a tree was 20 years ago. The second best time is today."
