I agree at least 12months old. My GSP is 4 this year and I would have swore she would have been a natural retriever. As a tennis ball is her constant companion. I have close friend who is proffessional trainer he told me she can quit me at any time if she makes her mind up to. Every bird I shot last year she would find it pick it up and look at me then spit it out. Blew me away. I was thinking is this the same dog that I took on a dove shoot at 9 months of age. So guess what. Trained retrieve it is!