Man, I spent one hour of my life the other day listening to an old Preston stream and he and his sidekicks were puzzled by why the alchemists' guild was 'replaced almost everywhere by the maesters in recent centuries'. They thought it was a Gurrm's fuckup since the last dragon died less than 150 years ago and thus the weakening of the pyromancers started only after that not in 'centuries' in the plural. They then proceeded to list other possible events that caused the decline of fire magic going so far as to mention the long night. It was the doom of fucking Valyria, god damn it!