The friend who stays interested after the outcome is settled cares about more than the suspense.

Uncertainty draws a lot of attention. People want to know what happens, and once it happens, they move along to the next open question. The person still asking a month later, when there is nothing left to find out, was interested in you rather than in the story.

Notice who is still asking about the thing that resolved in spring. Then go and be that person for somebody: check back on the appointment, the interview, the move, well after everyone else has stopped wondering how it went.