first of all welcome here. There is no improvement for lines in any age combination. It doesn't matter if you set a line only with old or only with young or if you mix them.
For a good performance the comination strength+experience+form (weighting .6 / .2 / .2) is important. Stength costs money (salary) --> https://www.eiszeit-manager.de/wiki/Gehalt Experience takes time or campcosts but for current costs it's cheaper.
Hello, is there some performance improvement on lines average age? In real life usually players peak at 26-32 years old and it might be in this game that if average age is around 26-28 the line is better "Best combination of youth and experience performs better"
I am very new to this game and want to learn about the little things that can improve my team.