I STG that Neo started doing the nasty when he was only about 10 weeks old! He was a very dominant little boy then and now! We wound up buying him a "phucky duck" for him and he abused it like crazy
(lol). Actually I understand that humping for the males is healthy, that it helps the testicles seat themselves. That helps especially if you plan to have him neutered, as the vet won't have as hard a time with undecended nads.