My mare is smack in the middle of her "good" years, at 27 years old.
I got her when she was 23, nearly 4 years ago, so I'm getting the pleasure of sharing her golden years.
She's still in relatively hard work for a horse her age. We go on 45 minute-hour long trail rides, w/t/c/g, about 2-3 times a week and she (with a little help from me, haha) gives w/t lessons to a couple kids a few days a week.
I think part of why she's so sound and everything (never had a lame day, she's had days where she got trimmed too short n' such but nothing structural) is that she nearly killed a guy when she was 10 (he was being stupid and Lacey doesn't like stupid) so she was retired from that day on until I bought her. Of course, they didn't tell me about that until I had put a lot of work into her.
She needed A LOT of training when I got her, and luckily I was able to train her, so I'm just now starting to reap the benefits of having a really reliable older horse. She's still very opinionated and I feel like she'll always be that way, but it makes her fun.
The things I'm extra careful to do due to her age are keeping her as fit as I can and I give her a really long warm up before I ask her to gallop or doing anything unduly stressful on her body. I also make sure to not let her get too tired. I worry that she'll get too tired one day and end up injuring herself because of fatigued joints. I guess you could say I'm just a bit overprotective. haha
I also make sure to blanket her all winter. I feel like it's a kindness to her because, although she'd survive being unblanketed, she's happier blanketed.
Basically, my motto with her is: after she's gone, am I going to be happier knowing that I stuck to my guns about not blanketing if shelter is available, or that she was always clean becuase I never let her roll in mud, or whatever, OR am I going to be happier knowing that she was snuggly in her blanket all winter, or had a great time rubbing the mud into her fur after a ride, or whatever else makes her happy.
I choose the second option, so basically I go out of my way to create Lacey's life in a way perfect to her. For her, that means being blanketed all winter, living alone with 2 llamas for a little companionship (she gets shoved around by other horses and then she gets depressed), having little kids come see her all the time, getting to roll after every ride with me, and just being loved.
I figure that she's lived this long, she deserves it!
She's a real sweetie... I hope you won't mind me attaching a picture... :)