Labeling from a many to many relationship class

I have created a many-to-many relationship class for our sewer mains showing the years that they have been cleaned. I am looking at labeling the years cleaned in a map and can't figure out a way to label all of the years of cleaning. We would just keep the last year it was cleaned, but would also like to keep the history of the cleaning. I am very new to Python and wouldn't know where to start to get something written that way. We are using ArcGIS 10.1 with a file geodatabase. We will be doing this with a few other items in the future, but may avoid doing that if we can't get this labeled.

Thanks to everyone for your help!