I have noticed that some older GKs do perform better too (and are more consistent). But some, 'old' or not, have still performed badly. In my opinion, it is all about the 'internal' hidden thing(s) that regulate(s) how good a player actually is and good he will be in a particular season.
Or the game just translates from real football — since most keepers are in their prime at a very late age, mostly 29+. In this game the number is 25.
AH AH — manager of Atlético Kolkata. Named in honour of my hometown club, Atlético de Kolkata, which won the inaugural edition of Indian Super League in 2014.