Keeping a selenium meter cell covered when not in use does extend its lifespan.
Rather than get an old leather case, just get a modern, synthetic photo equipment wrap to store the camera in when not in use. It helps, does not attract dust, mold, or fungus, and can be washed.
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I have a couple of Retina cases, most probably needing a bit of repair work. They're pretty but i only use them for brief periods when carrying the camera to protect it in use. If you'd like one, let me know and I'll see what i have that'd be usable.