The Naked Chicken Chalupa was one of Taco Bell's most successful product launches, and yet, it was only available for a brief six weeks before disappearing.

It's back now, but will only be available for a couple of months. Even with such initial success and hype over the Naked Chicken Chalupa, whether it will ever become a permanent menu item or not is still in the air.

Photo courtesy of Taco Bell

It turns out that fast food chains in general, including Taco Bell, have complex systems that determine whether an item can stay for good or come back in periodic intervals. Taco Bell's Manager of Product Development, Rene Pisciotti, broke down his company's process:

"Everything that goes on menu for permanency or LTO (limited time only) has to serve a purpose. It has to fill a consumer need or gap. What we [also] need to make sure is that the consumer experience is the same with that product day in and day out. If there's any jeopardy of it being different, not being made right or executed properly, unfortunately we have to take it out of consideration for permanency. The second consideration is where this product lies from a sales standpoint. Meaning, if I buy that, am I choosing to buy something different, or am I buying that alongside what I usually order. If they can both live in harmony, that's fine, but if there's an impact to ingredients and their quality, then it becomes problematic."

With the Naked Chicken Chalupa, Pisciotti's biggest concern is that the fried chicken shell makes it a tough product for Taco Bell staff to make. The extra labor and ingredients make it a little more challenging, but if the demand rises and operators can consistently punch them out, the Naked Chicken Chalupa could merit consideration for a spot on the permanent menu.

Photo courtesy of Sonic Drive-In

Taco Bell's not the only chain going through some considerations with their most buzzworthy items.

Sonic Drive-In just brought their Signature Slingers onto the national menu for a short period, and the next steps for them is to consider whether it'll be a permanent item or not. Culinary Director Scott Uehlein told Foodbeast that the Slinger will "have to earn its way" into that spot.

For the Slinger to hit the full-time menu, it needs to sustain sales once the advertising campaigns around the mushroom-blended burger subside, Uehlein said. That will establish proof that the burger can be successful on its own, making it worthy of consideration for a continual duration on the menu.

The Slinger is unique for Uehlein's team because of how groundbreaking it was upon launch. Nobody in fast food had considered a blended burger up to that point.

Uehlein said that the Slinger will have some extra, in-house considerations when the team decides whether to give it an indefinite spot in their lineup.

Photo courtesy of California Tortilla

While Taco Bell and Sonic tend to launch items for a limited run prior to permanent consideration, other businesses look at current items to see if they should be continued or not. This is the case for California Tortilla, an East Coast fusion burrito chain. CEO Keith Goldman's menu concept merits the more continuous cycle of LTOs, as his restaurants bring in flavors from all over the world, like Korean BBQ or Chicken Tikka Masala.

Goldman is continuously rotating new LTOs through his lineup every 12-18 months to keep customers excited, but also utilizes it as a testing ground for permanency. "About 60 percent of our current menu was a limited-time item," he divulged. He does have some criteria outside of success that are evaluated when he's thinking about making an item permanent.

Simplicity in operations and recipes is a big one, so that staff across all of his locations can replicate the product perfectly. Seasonality can also be a factor for Goldman, who runs a Bangkok Shrimp option on his menu throughout the summer for something customers can look forward to annually. It helps him build customer loyalty while maintaining a constant stream of new customers enticed by the latest limited-time offering.

Across these three chains, a consistent pattern of success, functionality, and ease of operations exists when considering whether to make hype fast food items permanent.

Nonetheless, customer demand continues to be a huge factor on all accounts, so if your favorite item keeps leaving and coming back, just know that there is hope for it to stay on the menu for good one day. The chains just have to figure out how to manage demand, and flawlessly incorporate them into their systems first.