DH & I have not pre-planned our Funeral at all....but DH's bro dropped dead at the age of 50yo in Jan of 2001. My DSIL upon picking out and ordering the Headstone for DBIL, she wanted this lovely huge stone. The stone company said they would give her a fabulous deal if she were to add the names of all those also being buried in the same plot. (My IL's have their very own family (generations and generations) cemetery in CT).
Well DH & I agreed to have our names on the stone with birth dates and nothing for (obviously) the death date. (To help offset the cost of the stone.)
Unfortunately in Nov of 2001, DH's father died suddenly. I will tell you my two young sons, when arriving at the cemetery to bury their grandfather, where absolutely FREAKED when they saw the Headstone with our names on it. They both commented how absolutely uncomfortable they were seeing their parents names on the stone.
Since then, we have done nothing other than our WILLS. They are completely up-to-date.