Here are my thoughts on older players.
Experience does matter. I've won a lot of close games with my older players leading the way. Lower experience players tend to make more mistakes and at bad times. With my old team and playing a team of equal skill, I am confident that most games I will come away with the win.
Having a trainer with career extension is important. No use having older 33+ year olds without that trainer.
In div 4/5 having 33+ players is important because cash is less available. The cash also needs spent on the arena so it just make sense to get older players to make more use out of cash. Also important is that when a player loses skill his salary drops. With lower salary players in div 4/5 this doesn't matter as much. Once you start purchasing players with more salary a player could lose up to $2500 in value just by a skill drop. However, with salaries below $20,000 this will not happen. The key is lower salaried players can absorb skill losses more economically than higher salaried players.
In Div 2/3 players need to be bought at lower ages somewhat. This is because of higher salary. Secondarily in those divisions you are less cash strapped as you spend less on your arena/draft and can devote more to player salaries. Also as you get to higher divisions you need to start pressing to get good trainees in place that can play starter minutes. This will require a bigger investment up front but will payoff when they playoffs come and your player has a more efficent salary as compared to non-trained players.
So for me, I used 6 players above 32 to win Div 4 with my only rotation players below 31 being my trainees. However in going to Div 3 I have now added two players below 32. I can afford to buy these players up front as I make more each week and do not need to spend money on my arena as much. So I now carry 4 players above age 32. As I look to win the title next season, I will probably add 2-3 players below age 33 with higher salaries and reduce my holding of players above 33 further.
So age of players is something I consider as important. It really drives the market. If you need a cheap roster and want to save cash for arena it makes sense to buy older players. As you progress up divisions though adding starting rotation youth is useful.