Cemetery follow up

Following extensive research (Sarah asked her students about it) I can confirm that Poles do indeed rent the plots of land that they are buried in.  It's not for a maximum of 40 years but this is about standard, the families of the deceased can opt to pay more and keep the plot for longer.  This implies that when the time expires graves are dug up, but I don't have any more info on this.  When Sarah and I walked around the cemetery a couple of weeks ago, we did notice that very few graves were more than 40 years old, and those that were tended to have another family member buried in the same plot more recently.