Header wraps will retain moisture and cause the above problem. Not a huge issue on an off the shelf header; but this could be a big problem for trick, one-off, super money headers. No one mentioned a ceramic coat INSIDE and out. I think sending your headers out to be coated in and outside will push the heat farther down the pipe. This will also fight corrosive compounds that the wrap retains. However, pushing that amount of heat farther down the system may cause damage elsewhere unless addressed (Stainless downstream of the headers). And the lowest point in the system will retain moisture/ corrosive compounds, so plan for that and make it easier to remove. If you have an X pipe or Cross Over, make sure its flanged so you can work on half the system.
If you value your headers, ceramic coat both the ID and OD. Im not a 'Jet Hot' brand fan, but that's just me. Do not drop them...its ceramic and sounds like you dropped your favorite coffee mug, except it costs a LOT more to fix.
Thats the guy that used to do a lot of work on our race snowmobiles (Dyno Port inc.). I used him because he's local and I felt comfortable with his recommendations.