How good a record is good enough? In truth, I don't think we even know enough to get the order of magnitude right. The best I can offer is that you need to record as much as you are willing to. The more you record, the more there will be to work with, and the less chance there will be of insufficient data. It may turn out that you simply can't record enough to create a good restoration of a person from writing, but this is little different from the risk in cryonics of not being well preserved enough to restore despite best efforts. If you're willing to take the risk that cryonics won't work as well as you hope, you should be willing to accept that writing yourself into the future might not work as well as you hope.

I think you're equating the relative risks here. If I wrote about myself for an hour a day for the rest of my life, I would rate chances very low that I could be reconstructed in contrast to cryonics. Your chances of being reconstructed increase with the amount of information present. One of the arguments for the safety of vitrifying the brain is that because the brain has a lot of redundancy (structure), we might be able to reconstruct damage.

I worked for a while in cryptography, where we try to recover original data wholly or partially from encrypted data. Based on those experiences and talking with Peter de Blanc, I looked into this reconstruction problem for a couple of hours at one point. Off the top of my head here's some tips which might make it easier for me to reconstruct your body, brain and memories if I'm alive:

Record lots of data. Speech is better than writing. Include at least one photo. Videoblogging should record at a ate of least ten to a hundred times faster than writing, and if storage stays as cheap as it now it'll survive. Freeze a DNA sample (cheap, but riskier) or record one (expensive because you have to scan it, but less likely to be destroyed). This should allow one to reconstruct a physical twin at minimum. I'm going to stick my neck out here and say don't censor yourself if you're recording audio. If I want to reconstruct your brain, the first step is probably to reverse-engineer your thoughts, so the more freely you talk the easier to deduce how you arrive at what you say. For example, I would learn more about someone if I watch them solving a cryptogram for ten seconds, than if they just gave me the answer. I have no idea if free association is equally as likely to work as essays. In general, the closer to the source the better in reverse-engineering: I've heard an estimate I buy that a minute of high-quality video could replace DNA in a pinch, but would still pay to freeze it, myself.

A friend of mine made a design for a $50 EEG cap, but the bandwidth is low enough that I doubt it's worth the cash for most people. If you have money to spare it can't hurt.

I wouldn't guess I would be able to exactly reconstruct so that you'd notice no difference, which is my personal standard and why I'm not doing any of this myself.

Ciphergoth, I'd be interested in what you have to say about this.