The conversation saved indefinitely can preserve a version of closeness that no longer exists.

An old thread holds people as they were at the time, at their most attentive, at their easiest with each other. Reading it can be a comfort, and it can also become a way of keeping something going that has already ended or changed. The archive is accurate about a period and says nothing about now.

If you find yourself returning to old messages often, notice what you are looking for in them. Whether that leads to reaching out or simply to letting the thread stay where it is, both are reasonable, and neither has to be decided this week.