We just buried my Mother In Law - My father in law wouldn't pay $500 to take her on vacation, but did pay $15K to plant her in the ground. Such a terrible waste of money and resources.
Oak caskets last longer in the ground. However, changes in temperature and moisture will make caskets susceptible to deterioration over time. Vaults can protect the casket from the elements. The body of the deceased will succumb over time due to decomposition and internal gases. Embalming helps, but not forever. What happened to the person that caused death has a bearing on how much longer the body will last.
