Once you are castration-resistant you will continue to live for one to two years. Sufficient time to make plans for the end. If your wife does not want to make plans now, there is no need to do so yet.
Two minor quibbles. First the good news. I think one to two year survival after MCRPC is on the low side these days. Three to four years is probably more up-to-date. See link below.
My second quibble is the bad news. Just because we may have an estimate of our time before prostate cancer gets us doesn't mean something else won't get us first. . /www.sciencedirect.com/science/article/pii/S030228381201559X