Tom,
Just to be clear, my maintenance practice only includes topping off the cells with Distilled Water. The fluid should only touch the bottoms of the 'spouts' under the caps. (maybe 3/4" from the top) If overfilled, the charging system will spill the corrosive acid out, onto your nice battery tray or car body, and cause it to rust. (Fortunately, Honda installs a plastic catch tray under the battery, but why take a chance???)
I have a battery hydrometer but I haven't used it it in maybe 15 years.
Often, on today's Maintenance Free (

) batteries, we need to cut or remove a sticker that covers the caps on top, in order to remove them.

In my experience, the cells on either end of the battery need water most often.
I'm getting 7 or 8 years out of even the small Honda batteries, and I replace them soon as I notice slow cranking during a start.
BTW, here's a nice gift for us battery maintenance freaks:
http://tinyurl.com/p99z3kh
It has a spring loaded nozzle that only dispenses water when it is pressed. NO SPILL!