Like anything you like, your desire for it can wax and wane over time based on a lot of things.
Look at it this way, perhaps there is a sort of food you love.... oh say Turkey Club Triple Deckers. So you eat a ton of them over a month or so, because you can. After a bit you start to not feel like another Turkey club. It not that you have stopped liking them, or dislike them now, its that you have had enough. So you take a break for a bit. A few months later the idea pops into your head *I'd like a Turkey Club!*
Much the same here. A fetish is simply a enjoyment of a non standard sexual activity, and like any sexual activity you don't NEED it to live. If life gets busy, or you have other outlets, or even been able to indulge as much as you like for a period, and so on, your interest may dip, as its being covered by other things. It will return after some time.
Now one fetish CAN be eaten by another fetish. Where a new like surfaces that is stronger then the old one, and you start to focus on the new one. You still like the first, but now there is a stronger pull in another direction.
Myriads