I have a small group of people where Christmas is usually our only contact, scattered all round the country. We like to keep in touch, even if it's only touching base - I've known many of them for over 30 years. If I send a card but don't hear back, I'll send for a second year then leave it - people don't always tell people they've moved, or if anything has happened to them, we're unlikely to know. I put a return address on the back of those cards, just in case.