Hey,
I really don’t want to go thru’ the pain of getting the old tip out of the iron again - I have the usual selection of RR lubricants, but nothing explicitly ‘hi temp’ - I found a couple of products that claim to do the job, but they’re pretty secretive about what they are 
Any ideas appreciated,
Thx,
Ian
[One thought was electronic heat sink compound…]
Automotive antiseize is the only way to go. Been there and done that! Fred
A product called “C5A” made by “Fel Pro” will do the job also…it’s the only anti seize / anti gall product approved for use in Nuclear applications…the mechanics in the plant I was in called it “goldfinger” and lots of distributors know it by that…it’s rated at 1800 deg F nominal, so it should do the job for you…you can use it on other treaded fittings as well…
The active ingredient in all of the above is molybdenum di sulfide, (mos2). Any product you find that has this as the main substance will work. It comes in powder,cream and solid form.
BB
Many years ago I had a little tube of anti-sieze for soldering iron tips. It was a brown gell and smelled like rotting fish when the iron heated up. Can’t recall the name of it. Lost the tube years ago and never had a problem with tips siezing up in my iron without it.
Get some anti-seize suitable for a automotive oxygen sensor. Any parts store should have it.
Jim