Hi norswap,
Author of Kill the Newsletter! here. That is a valid concern, thanks for bringing it up. I worry about this myself, being the #1 user of the tool. Do you have any idea how to fix it, though? I thought of a dead man’s switch kind of thing, in which I would periodically add an “everything is still working” for low-volume feeds, but I didn’t do it because I would consider such entries spam. What do you think?