[Syd Thrift]

It's not hard and fast but the aging/development figures measure how quickly a player ages or develops whereas the target age is more or less where development ends and aging begins. Speed and speed-related metrics (like outfield range, baserunning, etc.) basically start at 100% and only trend downward but otherwise if you wanted to, say, set things up the way people thought aging worked in like the 60s and 70s where a guy's prime years were considered 28-32, you could push the target age up.

IME if you want really old guys in your league the easiest way to do it is by dropping aging down. I have it at I think .8 for position players and .75 for pitchers and I do indeed see guys play into their early 40s. Often those guys aren't very good and the ones who are are always about to fall off a cliff, but they do exist and for me, more importantly, guys can be useful into their mid to late 30s.

(as an aside, yeah, guys drop off as well - I also have TCR set to 150 in my league - but I do think that IRL what happens is a lot of the time a guy getting "washed" at 35 is just a guy having a bad year and then never getting another chance after that. I know there was a study done on NFL QBs several years ago that found that roughly half the "aging" that occurred happened in a player's final year. This isn't to say that guys can't suddenly crap the bed - which is why I have TCR bumped up - it's just, you're going to treat a 34 year old coming off of a couple of seasons as awful as Jarred Kelenic's have been)