I used dvgrab to ingest my old tapes, and ffmpeg and avisynth/QTGMC to de-interface and encode files for easy viewing (though I keep the original .dv files).

The biggest issue I ran into was that while the audio and video were properly synced up in the original .dv file (due to it being an interleaved format), when I re-encoded the videos, the audio and video would drift out of sync as the video went on.

I was able to fix the sync issues by using dvgrab to split the original dv file into a bunch of 3 minute chunks. I then wrote a script to extract the audio track from each chunk, pad the end of the audio with milliseconds of silence to the exact length of the video track, combine the padded audio tracks, encodes the combined track, and muxes the fixed audio track with the encoded video. This worked really well; the silence padding is imperceptible, but the audio and video are still in sync - even after 2 hours.

A final point that needs making is that doing anything with dv files in ffmpeg (even -c:v copy) destroys the SMPTE timecodes embedded in the original file, making it much harder to split by scene.

Just because I've dealt with this exact issue in the past, it may have been a 30fps vs 29.97fps issue. For me the audio was a fixed length, but the frame rate was SLIGHTLY too fast. The problem can manifest as either too slow or too fast depending on which side is expecting 30fps vs 29.97fps.