Check with Dixie Gun Works or maybe Track of the Wolf, or Log Cabin Shop…
Tom

A touch hole liner should never be removed unless it's worn out and needs replaced. Depending on how hot the load is that could be any where from 3000 to 10000 shots.

I have no idea whether this is the case or not, but a builder of fine flintlocks once mentioned in passing that removing the touch hole liner frequently could result in wear of the threads, and that could lead to flame cutting following into the threads.

True? No idea. But I will say that I have seen both liners and nipples being ejected from their seat. Not often, but it only takes a time or two to leave a lasting impression! 

Ask Rick MacHale why he had the rendezvous nickname of NippleNose! 

I have been building custom flintlock muzzleloaders fulltime for a living since 1996. Hobbyist builder clear back to 1980. I have made nearly 400 guns. I NEVER put in a touch hole liner that has any way to remove it unless you use an easy out.
You'll wear out the threads screwing it in and out so I don't give my customers the option.  I can't imagine any reason to ever take it out unless the hole gets big and you lose accuracy.

mikebrooksflintlocks.com

I just received two, new flash hole liners. The gold colored one is installed and removed with an Allen wrench. Anyone used one of these? I am a little concerned it has no "head" to seat against the barrel like the steel one

I have never made a flintlock with a removable touch hole. I was the master gunsmith for Colonial Williamsburg and worked there for 40 years. Taking the touch hole in and out will cause the threads to wear and eventually cause gas cutting around the threads. I have made gold and platinum touch hole liners that last nearly forever, I know I have seen it. Your best bet is to install a White lightning stainless steel touch hole liner. They are sold by Jim Chambers Flintlocks Ltd. It will improve ignition and last till we are all done caring about it.
All the best.
Gunny