I’ve gone back to powdered detergent. It’s harder to find, but works very well, and is very cheap. I’m going to write on the box when I start a new one, but I’m sure it’s been at least 6+ months, probably closer to a year since I started this one. The key is to not use too much. You only need a very little bit. Most people use WAY more detergent than needed, and actually cause themselves more problems.
FWIW, though I rarely use tampons, the O.B. are my favorite. There’s no stupid plastic applicator. You just shove them in. And, they’re tiny. Live happily at the bottom of my purse, just in case!!