I've used a double adapter in the past, but have since stopped using
it.  My best friend's wife has a 2000-something Nissan Altima.  She
literally melted the lighter jack in there because she had a 3-way
adapter with all her electronic goodies plugged into.  I was
surprised to hear this, but was wondering just how much one jack can
take.  In vanagons especially, the jacks were designed for lighting
cigarette lighter, not powering laptops, GPS units, ipods,
cellphones, and the refrigerator all simultaneously.  I've toyed with
the idea of adding a second jack on a separate circuit to address
this issue, or beefing up the wiring to the jack.  I'm not an
electrician, however, and haven't done the research.

Does anyone know anything more definitive on this?

-Jarrett
89 Westy