I feed DTs a couple of times a week. My tanks are 6 months old and so far I have lost just one sponge (a yellow ball). A second yellow ball is in less than great shape (it likes to grow some algae during the day that gets eaten at night). A third yellow ball and my other sponges are doing fine.
After 6 months, I still have some barnacles that are alive as well as some other filter feeders such as a Turkey Wing Mollusk, small feather dusters, etc.
My nitrates are zero so feeding with it is not hurting my parameters. I probably should have fed more because I did lose most of my tunicates 8(. I do still have some sea squirts in my one tank that are fine.