Socks . . . Couldn't agree more there with you mate , Just because they look the part "Physically" doesn't no where near mean that they are "Mentally".
The young bitch that I have here that I bred, is a perfect example . . . Altho being 17 month's old is abit way off from fully Mature, she's had one term of being in season around 12 month's of age, and she's had abit of work so far this season, but I believe she need's another summer on her back before she can be classed an "Adult" in both way's