an addendum:

I tried recording continuously until the battery gave out. The PMD620
created a 2.7 GB file, proving that there is no 2GB file size limit
with this machine. Windows Media Player was able to open and play the
file. The recording (of household noises) sounded fine, with minimal
self-noise evident.

This demonstration shows that the PMD620 has good manners as it
approaches the end of battery life. The open file was closed and
saved properly as the machine shut down.

A 2.7 GB file represents about 4 hours and 20 minutes of WAV recording
at 16/44.1. Giving an allowance for extra time I spent with the
recorder powered on but not recording, and the fact that the OLED
screen was powered on the entire time recording was in progress, I
think 4.5 hours is a conservative estimate of the battery life when
using standard alkaline AA cells. Turning off the OLED screen could
stretch battery life another 15 minutes or so.

For the recording session, I used a Transcend 4GB SD card (not SDHC).
The PMD620 had no difficulty recognizing this non-standard card.

--oryoki