Plus, during those intervals, you will have the opportunity to "recycle" many of the rune shards into broken shards. I specifically target this as a feature to be able to complete the "circle" of runes for a new AW that I really want. By keeping an existing AW (or multiple AWs) at one of these levels (5, 10, 15, etc.), I have a pending source of broken shards to tap when I really need that elusive last one for a much wanted new AW.