it makes sure the bit reservior is unused at track boundaries

OK, I've looked into this a bit more in the Lame sources. It turns out it doesn't make sure the bit reservoir is unused -- it just discards it. So (a) keeping it from track to track in the car-player software doesn't win us anything, and (b) --nogap WAV files (if made all from the same command-line as nature intended) really ought to play back perfectly as it is. I'll do more research, probably with this album.

So you lose a bit reservoir's worth of data on each track transition, but you lose that on seek anyway and it's not always noticeable.

Peter