For the vocab 一生, WK gives this example sentence:
わたしの父は、しぬまで一生どくしんでした。
My father remained single all his life.
I can understand each part as far as I can see, but I wonder why 一生 is required at all in this sentence since しぬまで already means “until his death”. Is there a nuance or grammar rule that I’m overlooking?
I think without the 一生, it could be interpreted that he wasn’t single at some point, but then from some unspecified point he become single and then stayed that way until his death. Whereas with 一生, you’re making it explicit that he was single for his entire life. You remove any ambiguity.
Maybe it’s not required. After all, in English I could say
his whole entire life
even though I’m not required to say both “whole” and “entire”