I'm terrible at keeping in touch with old or distant friends, so this story doesn't surprise me.
Even though your friends may change, the number of close friends you have pretty much stays the same.
A team from Aalto University School of Science in Finland recruited 24 British students and monitored their calls for 18 months, to see how their contacts changed.
The research also suggests that we have an individual social ‘signature' - a distinct way of organising and maintaining our relationships. This year I'm going to work on mine...