It's a common misconception about D&D elves. Yes, for elf standards 39 years old elf isn't consider elf-mature. But for humans he is 39, like 39-years old human. Elves grow up as quickly as humans, they just grow old slower after then. So treat Astarion as en equivalent of 39-years old human magistrate.
Yeah I know hes 39 years old in anyones reference
My point was badly worded. I meant that he was unlikely to have reached a position of power such as magistrate much before he was in his mid twenties so probably was only a magistrate for something like 15 years at the most (give or take). And that as someone in his mid twenties onwards he was still a young man for that job by elf standards (actually I don't know many human magistrates in our world who would be that age, most are older).
All guesses anyway, for all we know he reached the position of magistrate and was vampired within a day for not being Cazadors choice for the position rofl
