Iunno. I've got some pretty old tires around....I'd be giving them a very good inspection and if I see any cracking, then yeah, they're not good. If there's no cracking, I am not too worried about it.
That said, at 10 years old, the rubber has degraded, so performance (grip & comfort) won't be what it once was.
Good quality tires, stored properly (indoors and covered) tend to do OK. I've got some 10+ year old tires that are absolutely crack free and I have zero stress over driving on them. I've also seen some 10 year old tires (like the 2011 date code off-brand units currently on the SLK) that are absolutely a hazard.