I've had mine for a little over a year (even growing them out in my pond in the summertime) and they are still only about 5 inches or so (I got them at about 2").
if you were in Australia, I would sell you mine... I have two at 7"... I have not had them for that long but I understand that they are at least 4 years old...
I call them algae disks, I guess they are wafers. Hikari makes them as well as others. either way, my kissing fish love them, I have to throw a few extra in so that my pleco gets some food. they also get frozen and live blood worms every now and again since this tank is also home for my bichir. they seem to like them, as do most fish. (fish can't resist the worm )