I was just about to say almost the same thing but I decided I'd check the other replies to see if anyone else had already said it. Just to emphasize and agree with you - I think most people imagine the 1st scenario when they are answering these questions. Its just too hard for people to imagine 40yr olds that are like 30yr olds, 60yr olds that are like 45yr olds, 80yr olds that are like 60yr olds etc... That is not what I think they are imagining when they are answering.
This new study by Pew Research on American opinions about radical life extension turned up some interesting results:
I also find the demographic splits on page 3 to be surprising. On the question of whether treatments to extend life by decades would be a good thing for society, whites are significantly less likely to agree: 36% of whites agree whereas 48% of Hispanics and 56% of blacks do. There is a negative correlation with age (48% of adults 18-29, 46% of adults 30-49, 37% of adults 50-64, 31% of adults 65 and older) and with income (47% of those earning 30k and less, 42% of those earning from 30k-75k, and 39% of those earning 75k+). The income result in particular surprises me, as my intuition was that people with a higher quality of life would be significantly more pro-life extension.