Several (yes, I know) non-scientific tests have suggested that if I can stay healthy, I can expect 92-100 years of life. Nice. Of course, anything could happen tomorrow (or today, for that matter), but I like being able to step back and observe this period of nearly a century against the backdrop of time and history.
As such, I'm taking as a optimistic goal of living to 100 for my personal life planning, which helps me plan conservatively, while also leveraging self-confidence and willpower. :) It's quite a bit of time, a lot can get done. By age 100, the year will be 2085. What will I be doing? Who will I be with? Where will I be? These are questions I suspect I won't know for some time... all the better, life should always have surprises.