Would you be here for it if humans aged at half the speed we do now and thus lived on average twice as long as we do now? Instead of an average death age of 75, we would live to 150.
I think that we would always want more. A lot of people today live twice as much as people a few centuries ago, but we live in the same 'pace', if you can call it that, and I think it would be the same if we lived 150 years. We'd get married later, probably graduate later, etc. It wouldn't feel any different.
We will always wish for what we don't have, and whatever we have, we will always want more of it.
Not sure. It would give me more chances to learn stuff and become a better person, but I feel like such a long time takes away from the importance of life. Individual moments matter much less when you go through so much more.