I think older people have a lifetime of experience to share if people want to listen. Especially interesting is if someone has grown up in times vastly different to our own, for instance my great-uncle, I was too young to listen to him firsthand (I did know him till I was 6 but he was always watching horse-racing in a cloud of smoke ) but my dad told my loads of stuff about his life, as a kid he'd worked in textile mills, getting the cotton out of the looms and later he joined the militia and was in both WW's. Older people are walking history books. Of course when it comes to life advice people often won't listen because they think the person is jaded and bitter, people usually have to find out the hard way and then realise the person was actually right.

At which age do you consider somebody elderly?
Early 70s I suppose, but it's just a case of people being older than you, their activity, mobility isn't governed by their age, nor are they necessarily going to be of frail mind or body even in their 80s.