The Stanford d.School style Instant Business Plan, where the elements are literally Post-Its than can be swapped and changed, is a far better north star than a one-shot document. I think the same approach could work well for a life plan: a paper document where changability is an intrinsic part of the format, but you are nonetheless forced to express your ideas concretely.
Hmm ... I think ... I think I might put this together with ideas from Ben's What you're proud of post and stick the result into my about page.