When is the optimum time to take a TEFL course? That is the question that will be covered mostly in this article, but I will also answer some related questions such as when you can get/start a TEFL job.
Now "when" in regards to taking TEFL/TESOL/CELTA courses...
Do TEFL certificates expire?
Well, they don't usually expire. Certificates are like any other certificate or diploma - they last indefinitely. However, if you take a course far from the time you actually teach then you are unlikely to remember anything from it.
So when is the best time to take a course?
As far as the certificate goes after you complete it you can put it on your resume. But for the training and your memory I'd say it's best to take one right when you start.
Before you start is good which is common, but you won't have much context.