Re: Why not cure entropy while we're at it?
The (unstated) assumption is that if we extend life, it will be either by just stretching out each period of life so you have more frailty, or by allowing the maintenance of life below levels of function currently achievable.
The 2nd is definitely wrong (or at least very implausible), as we haven't really changed this at all except in ICU, and few people actually spend their final days there, let alone months/years which is what we're talking about (at least, I am and I presume others are). The 1st is possible.
I think what is more likely is that we will extend the healthy lifespan - from age 70 to age 80, or to age 90. It is commonplace for me (and most doctors in developed countries) to look after 90 year olds who are still fit, active and enjoying life. (Because they need me to look after them it tends to all go pear shaped afterwards, but we'll leave that out of it :-) In fact, I am now routinely saddened when I see people in their 70s with multimorbidity as I feel they are "too young" to have such significant illness.
But I might be wrong. There's data to support both hypotheses: the extension of healthy life, with similar decline at the end, and extension of life with the same proportion of decline.
Either way, it's worth thinking about your lifestyle and considering the impact on your decline (ie stop smoking, eat less, exercise more). And when you consider your likely lifespan it's worthwhile making sure that you do things that aren't going to be achievable later (see you kids grow up rather than work).