There are quite a few factors - temperature, moisture, coffin type, body size, age that affects the decomposition times, but even if the average is 100 years rather than 10, my error is pretty small compared to those who are counting on there being something substantial to work with when the trumpets call, unless by fluke they have been fossilised.

The same processes that strip the bodies of wild animals to nothing in a year on the surface will eventually do the same to us underground - this was the point I am trying to make.