After taking a series of ion lightning hits, the shuttle loses attitude control and navigational systems. Janeway soon reports:
"Altitude: 12 kilometers. Hull temperature: 4,000 degrees. We have to reduce speed!"
That would seem to imply that they were nearing some maximum tolerance . . . though I suppose it could also refer to simply slowing down before colliding with a planet.
Also, in Mosaic[VOY], we get some Voyager-specific hull temperatures. The highest stated maximum is 17,000 degrees, though we do hear of minutes passing between the 14,000 and 15,000 degree marks, along with a number of minutes on the way up to 14,000. The hull doesn't boil off and there's no mention of permanent damage (though it does get up to 62 degrees on the bridge), so this is apparently a readily-survivable (though probably highly-inadvisable) hull temperature.
Also, I've updated the Tech Archives with some unfinished materials from Pathways and Mosaic, as part of continuing work on defining and dating the Cardassian Conflict (with the war still appearing to fall in the 2358-2362 timeframe). Check it out here.