I don't understand "it comes down to life expectancy". This is about marriage. The sentence before is : "Why get married with a justice of the peace or a minister?"
Does it mean : "if it all just leads to reduce life expectancy" ?
Thanks in advance for your help.
I'd take it to mean - if the only thing that you are concerned about is life expectancy (how long someone probably will live). This is hard to understand with the context we have so far. Is the speaker buying or discussing life insurance? are they worried about getting married because they are too old?
The speaker is speaking about his own marriage. He's trying to convince himself not to re-tie the knot and he's listing everyting's wrong in marriage. That's about all I can say with the context... Can that help ?
"It all comes down to life expectancy" means that life expectancy is the only important parameter to be considered; all other issues are irrelevant.
Once the reader accepts this fact, you don't need a minister (religion) or justice of the peace (government), you need an actuary to calculate how long you will live. Then you know if marriage is a good idea or not.