Ok, I finished playing (played through to the spring training of 2018) my first year of the Twins on Build 18.1.33 with lessened aging effects... Batter aging speed and Pitcher aging speed both set to .800
and wow... the guys are REALLY not aging very much at all.
Way too much of a change, so I'm thinking that the game defaults are pretty good this year compared to, say, 3 years ago game.
Thought I'd pass this info on to anyone who's working through the game and hasn't finished their first year and wondering about this like I was.