Perhaps I made a mistake in using the LW taboo words "I don't know". Really, how much is probably a function of how fine-grained you want the restoration from writing to be. Since I think it's reasonable to assume decreasing marginal utility from additional writing, I think a good estimate is that something like the first 10 pages of an autobiography are worth about the same as the following 100 pages (assuming a uniform distribution of information, so not the first 10 pages of a typical autobiography that might go in chronological order). The more you write the better the restoration will be. How good that restoration will actually turn out to be compared to, say, a cryonic restoration, is hard to know because we don't actually know how that will turn out either for sure, but obviously I think it will turn out to be pretty good.