But as for your main point, I think that this is a false choice, in the sense that if you look back at what I was responding to, I believe that you will see that what my comment referred to, is that given the choice between me getting old together with my wife versus me staying young while my wife gets old and dies, versus me forcing my wife to stay young against her will... I'd opt for the first option, as I regard the other two as unconscionable.
Apologies, I didn't appreciate your nuance there. I thought of that hypothetical as so strange that my brain short-circuited as you answered.
Now what you are asking, or at least what you seem to be asking, is something that I believe I already acknowledged and addressed in that same post (or a post shortly thereafter). Specifically, I acknowledged the unappetizing prospect of both becoming invalid, as well as having to care for someone invalid for decades on end. Of course you would recognize, that there is a fairly broad spectrum of "invalid". If at some point, the spouse becomes so far gone that they have to transition to 100% inpatient care, then you are completely relieved of having to be the primary caregiver. Similarly, if you are both too far along in terms of being invalid that you both need some sort of live in nurse and/or caregiver and/or nursing home care, then again, there is no caregiving responsibility.
If you're capable of off-loading their invalidity onto others, I don't think that diminishes the point other than the 'hassle' of taking care of a loved one, which isn't really the main concern. Whether you're losing money to take care of them or
vis versa, the healthier partner is forgoing
something to care for the weaker. If someone is wealthy enough that they don't really care (either through private wealth or through social supports), it's still opportunity cost. Or, at least, one person has to watch the other be significantly more diminished and incapable. But, you're right, you were answering a weird hypothetical.
That's easy... I'd want to be the one to go first, 100% with no reservation.
Does she agree? If so, logically you have two options if you
truly prefer that you go first. Allow yourself to degenerate faster than her, or delay her degeneration. Without active management, it becomes somewhat of a coin-toss.
The point here, of course, is that speeding your own degeneration is not recommended. And, also, that she probably wouldn't agree with your choice. I see no solution but to strive to maintain the partner's health.