Thanks, guys! It worked. I've been using it for hours today (trickle-charging + playback) with no problems. It still gets warm, of course. I put it up on its side in case that might help.
(See update post below.)
How so?
I don't hear a difference between charging and not charging during playback. (I tested this by unplugging/replugging it while various music was playing.)
Or perhaps you meant the longevity of the Mojo's internal battery?
Basically yes, for me its more about longer battery life and less noisy charging, my Mojo has that annoying noise when charging from all the mains chargers I've tried.