Say hello to your new roommate
Most places in the US people buy a spot for their family member that is supposed to be everlasting.
In Europe however it's common practice to reuse graves. People buy a spot for however long it's expected for a body/urn to decompose. After that they can choose to re-buy the spot for another number of years if they so wish. If they don't want to, another person will be buried there.
27th April 2019