spree/spree — pull request #5085 by jordan-brough (2014-07-30 13:28:41+00:00)
Title: Default order_factory line_items_count to 1

This took 40 seconds off of the "core" specs on my computer (3min30s -> 2min50s). I didn't measure the other suites.
Given the speedup it seems like a reasonable thing to do for the cases where you only really need a single item.