Yep..The bountiful GS at the end of the month, is often caused by Res GSers not being available.

GSs are pretty much driven by insufficient reserves.

I used to basically do the job of Crew Tracking, Crew Scheduling and Training Scheduling at my job immediately previous to Delta (some who were there, remember the constant Death Metal from my office, and the stacks of Diet Coke that was left as a peace offering to not completely screw people)

In a properly manned category, we would have enough on RES to cover all 12-24 hour out needs, and by enough, I mean guys on call, who can cover the whole trip (talking 3-4 day Domestics) and enough on Short Call to cover the last minute "oh crap, Dave got into a accident on the way to the airport, Mark woke up with the runs"

If we were properly manned GSs would only really come into play in no-joke real IROPS, such as "LGA shut down for WX on the same day JFK is on single runways ops, DTW and MSP are de-icing with reduced arrival rates for snowplows" not "oh, we ran the op a bit hot IROP"