In the last few years I think I read some horror stories about trained linguists who were put in slots that didn't use their skills -- they were ordered to pull guard duty, drive trucks, etc. I don't know if that was true then (maybe my memory is faulty) or if it's true today.
68,
I wasn't a linguist. But I was an enlisted man, and did work an intelligence MOS.
And I spent my whole 4 years active with tactical units, and spent a ton of time driving trucks, buffing floors, cleaning latrines, and the like. Doing actual MOS-specific work was relatively rare.
I would hope it's different for linguists, but I have my doubts...
Well, many trained linguists are detailed to tactical intelligence units that may have a broad theater of operations. In that case, you might end up not using your language for a full two years or more. If you're not experiencing consistent exposure to these very difficult languages, you'll atrophy.