Many years ago I was given a complete truck 8 3/4" with 3.91 SG and tires. Rather than tear it apart I decided to leave it complete until needed and parked it along side my shop. Years later I pulled it apart because I had a use for the pumpkin and I found about 1/2" of water in the bottom of the housing...enough to rot away the bottom two teeth on the ring gear.

Although completely sealed from rain, I surmise condensation was the source of the water. Use 'em or lose 'em.