https://www.jim-butcher.com/timelineEb is 400, and I think Ancient Mai is nearly twice that. It's more than 200 - 300.
"BEFORE 1600 (Over 400 years ago): Ancient Mai is born." "CIRCA 1700 (About 300 years ago): Ebenezar McCoy and Arthur Langtry (The Merlin) born." - DF Timeline.
40. The books are structured internally for roughly 1 year gaps, but he stopped writing them that fast years ago. Harry in fact may not be 40 until the next book.
"14 ASF, July: Peace Talks and Battle Ground" - TL. Harry: "AGE 25: Storm Front." - TL. So Harry's 39 in BG.
What I find weird is when he lists out the complaints of 40 year olds like their knees going bad and I can't wonder about a magic system that allows you to live for 200-300 years old all as a 50+ year old apparently.
Tall people have knee problems before regular sized people. Things can pop and crack from standing up in your 30's. Things start to hurt "for no reason," probably meaning damage you've done to yourself that was too minor to notice at the time plus some more of the same as opposed that thing that's hurt since high school because of that injury in high school. The way wizards work, you've probably accumulated too much damage to feel like you're 25 but you heal enough to keep feeling like your 50 instead of older for a few hundred years. So the injury from high school goes away, but the stuff you've done, mostly daily wear and tear, in the past ~35 years hasn't gone away yet.