Decades ago, there was a young man who joined the Rochester chess club where he had the frequent opportunity to play against USCF Life Master Dr. Eric W. Marchand if my memory is correct.
Who was that late starter? He became a GM in a relatively short time.
Many chess players who go on to become GM's have started out in the first few years of their lives.
Which late starters have been able to become grandmasters?
Please note that this question is the opposite of the more general "how young..." category of questions.
Dr. Marchand was not a GM, my error, he was a USCF Life Master.
My point is having strong competition can help one's chess development.
Also, it's fair to consider a late starter as someone who is perhaps age 20 and up.