I would just change them about every two hours, and I never had any issues.
Eighty percent of women use tampons now? Forget that crap.
Today, Tierno estimates that 80 percent of U.S. women of menstruating age use tampons. But as Keighley notes, it’s a mistake to assume consumer habits are the same everywhere. For example: Outside North America, digital tampons have outsold applicator tampons for decades. “If you interview women in Europe and ask why they like digital tampons, they’ll tell you about [environmental] concerns. They’ll also tell you that it’s a hygienic concern—that they don’t trust the applicator being inserted inside their bodies,” Keighley says. Conversely, tampon users in the U.S., who largely prefer applicators, “will tell you it’s a hygienic thing—they don’t want to gunk up their fingers,” he explains. “Consumers develop very strong opinions on usage habits—polar opposites, for the same reason.”
There is no way there can be a "safe" tampon. You have to change them regularly, at least as often as pads, and of course they are potentially far more dangerous than pads.