I must say I am sad to see the old boarding passes go away. I have saved over 1500 of those stubs(don't ask me why) and the flimsy paper is just not the same. I kind of enjoy leafing through them once in a while and reminiscing good trips.
Better take a close final look at the older ones. They're thermal as well and the printing on them is not-so-slowly fading away to nothing.
The new thermal paper ones degrade even faster. Sometimes in just one day if exposed to extreme heat.