Gennerally speaking a dog is considered a puppy till its three years old then it becomes an adult but most dogs live around 15 years on averege so probably 7-10 is like middle aged I guess.

Is this statistic true that most dogs live around 15 years? I hope it is the case but it seems quite high to me?

Don't think you could really apply an average when different size dogs tend to have different lifespans. I've had GSDs live up to 14 but this is a good age for a large breed. Smaller breeds have less strain on the organs and tend to live longer, so I'd say 15 was certainly a reasonable age for smaller breeds.

Very much depends on the breed, personality and health of the dog.

My lab is 8 and I can't really see any signs of him aging yet. He doesn't bound straight to his feet after a long sleep anymore (maybe the early signs of creaky joints), but he will still run for miles and will never turn down a walk.
He's also not got too many grey muzzle hairs - I've met black labs with totally white muzzles, only to be told that they're 3 or 4! I think because of this he is often mistaken for being younger than he is.

Overall, I consider a dog mature at 3 and senior at around 7-10, depending on size and the individual. However, I don't believe that this has to mean a change in lifestyle (except maybe senior food). As long as the dog is happy doing what they've always been doing, I see no reason to change

If this mystery girl is who we think she is, she'll be 12 in July!
Do you think she's old...?! (She might look it, but she doesn't act it!).

I have a 10 year old, 9kg crossbreed bitch. She is both physically and mentally fit and healthy. She isn't on senior dry food yet either (though she does have a varied diet, she doesn't just get dry food).

I also have a 7.5 year old Westie who is also fit and healthy with no problems.

Depends on the size and type of the dog really, but I wouldn't consider any particular age specifically to be 'old' and 'middle aged'.

As far as I'm concerned, my 10 year old still gets as much exercise etc as my 7 year old. She isn't yet showing signs of slowing down. She is also still a P.A.T dog, does a small bit agility for fun, enjoys playing with her ball and generally running riot with her pals.

Louie - ugh still very much a puppy at 9 months which I love but if that bloody 13-16 year old doesn't vacate his mind and body soon, we're going to have issues

Benjie - he's around 6-8 years old, very much a grumpy Granddad - apparently he always has been since they got him at 9 months old. Loves his walks and will no (after 7 months!) play chase with Louie in the garden.

Sadie - 9 years old, you try and stop her. I always call her my old girlie but when people guess how old she is, they are always wrong, they always guess at least 3-5 years younger than what she is. She can give a few pups a good run for their money.