Friendship, like love, is destroyed by long absence, though it may be increased by short intermissions.

Closeness runs on shared present tense: what happened this week, the joke that only makes sense now. Gaps of the right size make that material fresh again, while gaps long enough for both people to change unobserved leave two friends fond of who the other used to be. That is why some old friendships feel warm and slightly empty at once.

Distance is survivable as long as the contact is not also occasional, so keep it small and regular rather than saving up for a proper catch-up. A short message about something ordinary does more than an annual summary. The aim is to keep sharing the present rather than reporting the past.