To keep growth up just keep adding organic matter/compost every year and fertilize if the plants need it. Many of us use the same spot year after year without disease problems. In a home garden you can gamble that way, and only rotate after a bad year, but if you are a tomato farmer you want to rotate your crops every year to be sure that you don't loose money from a disease outbreak. Removing diseased leaves from the plants/garden also keeps the likelyhood of disease the next year low. Farmers can't do this so they have "dirty" fields and disease buildup.