Please do correct me if you think I'm wrong. It's off-topic but I just want to make it clear what I meant.
As an expat, it is unlikely that you are hired to perform all your work entirely in Japanese. This was what I meant by 'speaking' and 'working' in Japanese. It is more likely that you are hired for a certain professional skill you possess (e.g. engineering/IT), which is most likely going to be performed in English. I'm not saying that you will not be using Japanese entirely in your daily life. Anyway, this detracts from my main point. What I had intended to illustrate was that it is unlikely that he 'won't be able to last a year there as an expat' because he would not be subject to all facets of Japanese work culture and expectations as he's working there as an expat, not a local. Cheers.