Olivia did it at 10 1/2 - 11 mo and it was great! Alex not until about 15+ mo but she was always a bigger sleeper than Liv (like you, i knew liv woudl drop naps early and i expect her to drop napping alltogether earlier than alex - who is currenlty at almost 3yo still napping 1 1/2 - 3 hrs daily)
any time from 9-10 mo woudl be in the realm of "normal" wth the average/ most common being around 12-13 mo and some not until 18 mo