בן חמישים לעצה
Among the list of landmarks Rabbi Yehuda ben Taima lists in psychological development (Avos 5:21) is “בן חמישים לעצה — a 50 year old is [ready] for planning / advice”. (This is 10 years after “בן ארבעים לבינה” — that 40 year olds are capable of comprehension.) Generally this is taken to mean that when someone turns 50, they should have gathered enough wisdom to be able to dispense useful advice.
I would suggest the tanna is praising a higher level of development:
“a 50 year old is [finally ready] to ACCEPT advice!”