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Nikon recommends that the battery be removed if the camera is to be stored for an extended period of time. They do not specify what that time period is.
From D7100 manual
"Storage: To prevent mold or mildew, store the camera in a dry, well-ventilated area. If you are
using an AC adapter, unplug the adapter to prevent fire. If the product will not be used for an
extended period, remove the battery to prevent leakage and store the camera in a plastic bag
containing a desiccant. Do not, however, store the camera case in a plastic bag, as this may
cause the material to deteriorate. Note that desiccant gradually loses its capacity to absorb
moisture and should be replaced at regular intervals.
To prevent mold or mildew, take the camera out of storage at least once a month. Turn the
camera on and release the shutter a few times before putting it away.
Store the battery in a cool, dry place. Replace the terminal cover before putting the battery
away."
Also be sure to charge the battery before storage if goes flat you run the risk of killing it. Occasional use would be a better option to storage.