After harvesting a bunch of Pegasus stargates, McKay & Co. daisy-chains them end-to-end until they end up halfway between the Pegasus & Milky Way galaxies where they build the Midway Station. Then the same happens on the other half of the trip to the SGC with harvested Milky Way stargates, drastically reducing the time to get from Atlantis to the SGC vs. the long trip on the Deadalus at FTL speeds.
How long did it take to get to Midway from Atlantis via the Stargates? I guess it come down to how long the transit time is between two simple stargates?