Were Connery and Moore that young when they started their Bond careers? I honestly don't know. I think Craig was the youngest Bond if I had to guess and IIRC in Casino Royale he was supposed to be just starting out as a 00 agent. 50 is fine IMO and it's not like he has to do a lot of films before they switch it up again.
Connery, born 1930 had his first Bond role in Dr. No released in 1962. He was 31 during filming.
Moore, born 1927 had his first Bond Role in 1973 at 45.
Craig, born 1968 had his first Bond role in 2006. He was 37 during filming.
Lazenby was born in 1939 and made his one and only Bond movie in 1968/9. He was 29/30.
Lazenby was the youngest Bond.
Followed by Connery.
(Dalton was 41)
(Brosnan was 42)