I sometimes get Dan bones from the butcher but they are quite hard to get hold of sometimes and they tend to sell out, so if there are any I buy a couple and stick one in the freezer. He absolutely loves them and they keep him quiet for hours. Its quite difficult to drag him away from his to get him to go outside and then he rushes back. It keeps him occupied for hours, if not days! I think he was quite young when I first gave him one.
They sometimes get a bit smelly after a couple of days or so which is when I tend to take them. Some of them don't get smelly at all as he has had all the meaty bits off them and some he's still got MONTHS later! 8O He still comes back to them sometimes.
One thing, we do take them from him from time to time and give them back to him, as he growls a lot - we've worked out that it isn't being agressive or particularly protective - he comes dashing up to you, bone stuffed in his mouth, wagging his tail, but growling and shoving it at you! Its more of an excitement thing. But all the same, we make a conscious effort to take them away just after he has got it when he is still very excited to make sure he is not being too over protective with them. This may not be right but we like to know we can do it. He does growl but will give it up easily although I am a bit apprehensive about giving him bones when the children are around (they are my OH's children who come at weekends) and haven't done just as a precaution really.
I'm sure there are more expert opinions who will advise you about bones.
Bliss though! I gave one to Dan the other weekend when we were spending most of the day stripping walls - he just gnawed away happily all day
Oh yes, I actually took this one straight from the freezer.