Years ago (more than I'd like to admit), we had a PHD (might have been a vet too) that did his thesis on tapeworms. We got a lot of education during that talk One of the things he said was if you really wanted to do a good check for worms, you should take in a sample everyday for 3 days in a row.
so many of the greyhounds carry a worm load that I just worm them 5 days with panacur and do not do a fecal. I don't worm for tape until/unless I see them. The only time I do a fecal is if I suspect giardia.