Well, we're in similar, but not exactly the same boats then.....I'm 40 and married with no kids.
I too have been recently considering other employment options--still teaching, but in countries that pay a significantly higher wage. I know this thread isn't about my situation, but my point is that I believe we're at an age where it would be prudent to increase our capital. For example, I believe my peak earning potential will end in 5-7 years (probably 5), and I think it would be wise to take advantage of it. How long do you think the types of offers you referenced in the OP will be available to you?
Since you're not married and don't have kids, I'd go back for approx 3-5 years...as you pointed out, that will give you enough to live here for 9-15 years...which would bring you to approx 60 years of age....when you could then live off your investments and savings.
Three to five years is a long time in the snow though.
Just my two satang.
Good luck.