How should I store an L.C. Smith ejector gun long-term?

Insert snap caps and pull the triggers, then open the gun to eject the snap caps. With the gun open remove the forend; the ejector springs will remain relaxed. Now let the hammers down using a 'striker block' or snap cap. This will take the tension off the hammer springs.  Don't forget to cock the gun before reassembly. 
 
You might wipe down all metal parts with a TUFF-CLOTH and run a RIG No. 2 Oil soaked patch down the bore.