One large Catholic Church I hunted originally burned in 1905, then rebuilt. Folks came for many miles for well over 100 years to attend mass and held large picnics out back. I received permission from father Mike there (he gave me the ok to hunt the cemetery arcross the street too, I declined).
The 5 acre picnic grounds had been hunted heavily since the 80's.
Still, I dug several silvers including Barber dime, Washington quarter, mercs, wheats, silver ring...and best of all an 1889 Morgan dollar that gave off a strange signal at 3 inches deep. It appeared to have been slightly scorched by fire, and came out of the dirt brown-looking. When I first posted about it online, some said it was counterfeit. It ended up cleaning up good with a little work.
Other churches I have hunted have been slim pickings.