This question was asked at one of Dr. Grant Woods field day to the Eagle bean rep. He said you can plant every year without a break with no problems. I have a plot that I have planted for a straight 7 years and I have had no disease problems. Will be planting same spot again next year.
Here is some info I found yesterday (in between food comas) about year after year beans. It is even about a farmer who is about 125 mile from me. I am going to go to year round beans. From what I have witnessed from my corn vs bean usage with rye over-seeded, the beans are utilized later i the season, last into Feb, March and offer more nutritional value than corn. I have a very high deer density and my corn plots hardly make it to and never through December. I have 5 acres of beans in two plots.
I live right at the edge of heavy ag. The Missouri river bluffs are what I border up to with ag almost nonexistent towards the river(about a mile and a half) but ag is king starting at my property, heading west.