I understand you, I also would not sell my Vizner's pieces :-)
It was Frantisek Vizner who first time fully used the thick walled pressed glass designs in his graduate works. It gave to Czech pressed glass from sixties that special look and spirit - so different from imitation of engraved glass used in pressed glass designs before. Unfortunately temperature strains in thicker glass mass has introduced some technological problems - in fact easy solved with prolongation of time of cooling of hot pieces.
Fabrication problems had been solved succesfuly, but for us collectors not definitely. The internal stresses in glass can create the glass cracks after many years, the sudden change of temperature can induce it. It is easy physic or material mechanic but unfortunately another aspect rules - Murphy's law - the chance you will randomly loose your piece due to internal stress-strain crack is growing with the price and uniquiness of your beloved piece
No, no - joke only - in fact I have lost only about 10% of my glass collection in my wife's washing machine until I have discovered that this is definitely not the best cleaning method for thick walled glass