Canned tomatoes and other food should be good for up to a year, according to Ball's Fresh Preserving website. After that time they begin to lose nutritional value.
All canned food, including tomatoes, should be properly preserved and stored for them to have the longest shelf life. The jars should be completely cleaned before canning. The jars should be kept in an area that is less than 70 F. Also, the jars should not be frozen. If the jars are not stored properly, the taste and texture may start to change over time. The nutritional quality of the food may also break down. Make sure to label jars and always use the oldest jars first.