It would also work without Close() and still causes the desired side effect: GetSeries("QQQ_Breadth_Composite1")
It is worth noting that Aggregate Series are updated on the fly when referenced directly (or via formula) in a screen or live or simulated strategy. So in your particular case, you may leave out this extra reference.
Aggregate Series that aren't referenced directly in a screen or strategy will not be updated, and any other usages of Aggregate Series would show a stale series. So to that extent, Aggregate Series aren't updated automatically.
Notable uses that do not cause Aggregate Series to be updated are universe rules, ranking system nodes, and 'advanced' usages in higher order functions, (specifically, loop and historical functions). These cases currently require this workaround of adding a reference to the rules of the screen or strategy.