Is there any advantage to turning off full cemeteries? I have a ton of full cemeteries, how would I be able to best organize them and not cost me money.
Whenever a cemetery gets full, you should set it to 'empty' into a crematorium. If you have not unlocked this building yet, you should turn the cemetery off. It will no longer provide hearses, but will keep storing the dead bodies, and it will not cost you any extra money.
Cemeteries do not dispose of corpses (unlike real life, where eventually those buried in a cemetery are dug up and disposed of). So each cemetery is effectively a permanent drain on your available land. This has some consequences:
It is not possible to have a sustainable city whose population is high enough to require death-care, but not high enough to support a crematorium. The city will eventually have to build so many cemeteries it will turn into a necropolis.
Even when you get the crematorium, cemeteries still serve a useful function. Crematoriums can burn more bodies than they can transport in a typical city (the exact ratio depends on the density of your city and how efficient your transport network is). Cemeteries provide additional hearses for less money per hearse per month. A useful figure to go by is about 5 cemeteries per crematorium.
Each crematorium provides for 7 hearses, while each cemetery provides for 10. Cemeteries are also cheaper to run. Unfortunately for the mayor, a mixed configuration of both cemeteries and crematoriums requires some repetitive micromanagement to use, as you will need to manually empty your cemeteries every once in a while to keep it running at peak efficiency.
A crematorium can typically burn 200 per week in a mixed config, or about 20-40 otherwise (only crematoriums). Citizens live for about 6 years (about 250 weeks). Thus one crematorium can provide for a city of 50,000 (with help from several cemeteries). Without cemeteries, you'll need a crematorium for every 5,000 to 10,000 people.