Hey, I'm still working through all this and testing, wanted to throw this out there in case anyone has some feedback. What I'm doing is, at the end of a season: (1) age all players one year (2) for every active player, based on his age and position, calculate two values for every attribute (durability, speed, etc), increasePct and decreasePct. I plan on these being very small, with increasePct a little higher when they're young, and decreasePct increasing as they start getting pretty old for their position. Note that these differ for different attributes. So, for example, a great QB may not see his Leadership diminish even as he ages, but may start seeing his durability decrease or maybe his long passes. (3) roll the dice for every attribute and see if it increases or decreases In addition, your allocations into training and conditioning will affect the results during the season. Here's the important point, though. I don't think you'll see many changes each season unless a player is very young or very old, and even then you won't always see changes. My fear is that if I increase young players every season, that'll be unrealistic, and on the other hand, I don't want to lose players too quickly. The odds will differ based on age, though. There will be a higher chance of very young players increasing. One last thing. Since I currently have team values for offensive and defensive lines, I'll have to assign a random chance of them decreasing, and a small chance of them increasing. If they do decrease, you're going to want to address that in the draft phase. Let me know if you have any thoughts on this. I imagine the best test will be when it's in people's hands, though!