Biennials die after blooming... I've had people write to me at this site asking why their blackeye susans didn't come back after they dead-headed them... Well, the answer is that by removing the seeds, you removed the plant from your garden!

Of course, there are blackeye susans that will come back w/o seeds... Notably rudbeckia fulgida, better known as "goldsturm". I also find that rudbeckia triloba performs as a perennial in my deep south garden... but most sources suggest that it too is a biennial...