I think it's a great idea! I kept a hair journal like the one you described for about a year. And I didn't use it every day, but certainly most days. It proved invaluable to me after a few months because I could then go back and look at trends (one conditioner always performed badly when the dew point was below 40, one gel seemed to do best when I used it with a certain curl creme, etc.). We always thinks we'll remember what worked and what didn't, but we don't! The journal is the best way to document hits and misses.
But yes, it can be tedious. And ideally, you would do what Gills suggested if you have the time and patience. Like anything else, the more effort you put into something, the more good use you'll get out of it. So, for a few months of painstaking effort, you could be rewarded with a ton of very useful information about your hair. Good luck!
3a and strictly CG since August 2007. Porous and on the fine side. No to magnesium sulfate and glycerin. Yes to protein!
CONDITIONERS and LEAVE-INS:
Mop Top Daily Conditioner, KBB Nectar, Aubrey GPB or Island Naturals, Robert Craig, Any Jessicurl
Fuzzy Duck, B5 Design, MGA Scultping, BRHG
Fotki password: chuckle