If you don't have a problem I wouldn't Slime them. I have used it on my original Rokon tires when I first got the bike as I had leaks around the bead. Unfortunately I could never get the slime up around the bead so ultimately had to have bead seal put on. With my new tires I don't use it but I have it along when I go to the mountains "just in case". It is sold in all the ATV shops and the reports I have are that it does work. As Ed said, some repair shops won't work on tires that have been Slimed.
Pete