I can't speak for myself I believe I have worked with some contributors to LedgerSMB who are retired.
In general, I think one has to be careful about making generalizations here regarding aptitude. LedgerSMB is hard to get into because with ERP/Accounting software the domain knowledge requirements are significantly higher than the fluid intelligence requirements and domain knowledge increases as we get older. In LedgerSMB I have generally found that older programmers contribute better code than younger programmers precisely for this reason. Some of the biggest bugs we have ever had (the ones that caused us to pull 1.2.0 and 1.2.1) were caused by overlooking a critical part of domain knowledge.
So I dont think things get particularly worse. The fields of excellence may change however.
In general, I think one has to be careful about making generalizations here regarding aptitude. LedgerSMB is hard to get into because with ERP/Accounting software the domain knowledge requirements are significantly higher than the fluid intelligence requirements and domain knowledge increases as we get older. In LedgerSMB I have generally found that older programmers contribute better code than younger programmers precisely for this reason. Some of the biggest bugs we have ever had (the ones that caused us to pull 1.2.0 and 1.2.1) were caused by overlooking a critical part of domain knowledge.
So I dont think things get particularly worse. The fields of excellence may change however.