It wasn't necessary to create a disambiguation between 'EFL' and 'ESL' and then use the switch in the rebuttal. You know what I meant writing 'ESL in China' and I knew what it meant and we all knew what is meant by that. So now that isn't here nor there and we can discuss what's more difficult or requires more skills (EFL vs ESL) later I suppose.

As for a career. Again, not sure if you are trying to have another round of 'definition' here but what do you think 'career' means? The commonly understood meaning is the only helpful meaning and the definition you understood being used: making a living doing it. 'career' might even imply making a living and some kind of 'arc' or development over the time.

So, as I taught you earlier, many ESL teachers (EFL if you prefer) make a living doing this and yes they progress as they go along in some 'arc' or something we'd call a 'progress, steps, advancing'.

As you were recently taught - some (many, a few, 17,000) start at the bottom as ESL teachers in their home country (joking but not really) and that's relatively easy but they might earn a living doing it. Then they decide to go overseas to a 2nd world country and take on more skills and make a living teaching English in China for example. Often starting at some poorly run training centre. After 1 or 2 years they are making a living at a University or perhaps more upscale VIP lessons. Or even large adult audiences. From there many will take on the responsiblities of a 'Director' in some capacity for a training center or english department. After a few years some of these people move to Taiwan, South Korea or Japan and again continue earning a living and in many cases more experienced teachers earning a fairly decent living while now becoming skilled in many different Asian cultures. Its not unusual to learn these teachers have transfered onto Dubai and some Arab countries where they might even do surprisingly well financially speaking but are now becoming superb experts at how to teach 'EFL' to many different ages, levels, categories. Some of the great ones develop into very skilled entertainers I should add.

Now, at any given time many of them may be staying put somewhere or like many people in many careers sacrifice some financial betterment or progress in exchange for some new experience skills - maybe move to Vietnam to teach EFL or even choose to stay in a China training center but for legit reasons they reason.

Not unusual to find these people. I once read a statistic that some 17,000 westerners are 'Career EFL' teachers. They earn a living (usually fairly comfortable overall) and they do so for their life. Their long-term lifetime job.

So what about it?

Unless you want to change and use some specialty definition of career then you stand corrected.