Morning over here perhaps I am of a different mind set but every piece of burl I have turned has the potential to disintergrate being made up of grain running in every direction. I live in the land of Burled beautiful timber.
Reading so many turners rush to the conclusion it must be stabilised etc, this is the thought furthest from my mind, perhaps because I choose to turn only stable blanks that I store for a time to make certain at least they are dry eliminating all the factors inherent in blank failure I can.
Within a mile of my home is a wholesaler Burl getter with 15 ton at any time in his yard brought after travel, cutting etc he has 15 thousand burl blanks cut and dried as we speak, I have also learned if you can purchase burl blanks cut and dried good idea if you buy burl in bulk cut then yourself into blanks for pens you soon learn there is a bad percentage of losses firstly the bark accounts for up to a fifth of the weight you pay in the rough and so on then you lose 1/3 or more as it dries. The most stable burl is not near the bark.
Making pens from Burled blanks IMHO requires much more care in assembly tightness of fit into kit components and a necessary care when turning not to bite too deeply with the gouge kept sharp as being especially careful near the ends of the blank, care also in glueing facing the ends of the blank.
Australian burl is mostly very stable I regard brown mallee burl as bullet proof but I read continually on this site how awful it is to work with. As in all things you will pay for quality easy to see in burl I find.
You may also say I live near a Gold mine of burl and you are right however a cutter, wholesaler is never in a position to allow you to chuck hundreds of burl slices into a pile select one, have a yarn and disappear its his living and its a tough life.
I respect people like Curtis with his methods of stabilising suspect timber and encourage everyone to turn within your ability, I have never lost one pen to splitting ie a burl blank but I find African Ebony fearful to find clean split free quality as well as Snakewood and some others. Also I note the extremes you experience for example in the states of climate but hasten to assure you some materials in America regarded as completely acceptable and desired such as the tarred sandy roofing tiles extensively used there do no last very long in Australia my Church HQ is in America and all our earlier buildings were roofed this way , none of them lasted very long had to be reroofed at a high cost, horses for courses I guess.
Generalisations on burl use comes down to specifics all lead to experience but to make the same mistakes unwise and expensive.
Have fun with Burl I do. Later in the week I will take some pics of various burl blanks to illustrate the things I have said I may not be able to name them all as over time my memory fades and marks dissapear.
Kind regards Peter.