Longevity, honesty and loyalty are characteristics of close friendships.
Longevity is an important characteristic because close friendships usually need a lot of time in order to become intimate.
Honesty is also required in order for a close friendship to last, as good frienships cannot be based on lies. So, honesty is one of its characteristics as well.
Loyalty is another characteristic of a close friendship because close friends are always loyal to each other.
Tact and availability do not always characterize a close friendship because a close friendship can be maintained between two people without, for example, them being available all the time.