There seems to be, at least sometimes, a lot of talk on the internet about refreshing or reactivating a language. What that means is, for example, once upon a time you learned a language to fluency. Oh, you were good at it. Real good. You were fluent! In fact, when you were in country, if the police ever stopped you on the street for questioning, you could make up a story on the fly and the policemen would be so impressed by your fluency that they would enjoy your fabricated story with a little laughter and then let you go. But now, you have half-forgotten the language. You are rusty. You've just been invited by the local Elk's Club to give a presentation in your foreign language to the members who are recent immigrants to the country and afterwards you will be expected to answer questions in that language as part of an open forum. So what do you do? How should you bring back your language skills? How long does it take? Here is my opinion on the subject:
If you were ever really as good as you say, why did you abandon the language? One should not work so hard to accomplish great skill and then just abandon it. Languages are not just picked up and then tossed aside like... (I'll let you finish that sentence.) Spend just once a week to read an article in the language. That will be enough to keep the language at the tip of your tongue.
I've noticed how easy it is to forget the names of teachers I've had. It takes me about 3 months and after that I won't be able to recall the teacher's name. Other people remember the names of all their teachers they've ever had. Whichever category you fall into, a little bit of activity in your foreign language once a week shouldn't be any trouble at all. It will keep the language fresh in your mind and is a natural method of review. No need to go abandoning a language.