Yes, I definitely reformated the 8gb card before starting, it gives about 11 hours of capacity at 16/44.1. Also loaded a new pair of Duracells. This gives me 9 hours of battery life so I run them for 6 hours tops just to be safe.
So I started recording at 6pm and walked away. I'm at a festival with 3 kids so this is how I tape. In this case I have an intact file, 1.99gb just like a normal autosplit file, and the audio switches without a click, pop, gap or any other glitch to audio recorded the day before, right in mid file. The files recorded after that file are fine.
formatting your cards between uses?