I'd say Peanut, nearly 16, has stayed about the same in terms of play. Pretty much the same amount and in the same ways as she did when younger, perhaps with more naps? But I remember her always being a bird that would rest. Play hard then nap; repeat. She definitely hasn't lost her love of destroying stuff and manically chasing balls around.
Her interactions with me I would also say are nearly the same. She's about as aloof as she always was, some days she is more into doing her own thing, other days she will pester me continuously until she's decided she's absorbed enough cuddles (which is either never or bedtime, whichever comes first.) She's less spunky certainly, I used to get bitten every couple months now we're down to around once a year (nips don't count.) I attribute that largely though to me changing how I respected her, me avoiding making her feel like she needed to bite by changing how I did things. If I were going to ignore her instincts and desires I could get bitten every day.
For toys, the only difference I could notice is when she was very young (less than 3 years old) she would actually destroy pine and other sorta hard woods. I still remember when she hit sexual maturity and destroyed an 8ish inch pine ladder while I was in school, I got home and there were just two steel hooks handing from the perch where the ladder was, a couple dropped dowels, and sawdust!
Even as a middle-aged birdie she had already lost any interest into putting that much effort into shredding wood. It's been pretty much the same preference for the last decade: balsa, yucca, and anything else soft enough to really sink her beak into. Also anything paper, her desire to build nests has never waned.
Treat preference has stayed the same as well. She still worships at the altar of her lord, The Almighty Millet, daily. New foods and treats have come and gone but her old favorites are all still favorites. Peanut has always been a bit odd as a lovebird who prefers fruit and I've always wondered if that would change in time, but nope.
I would wonder about other senior birds too though! Peanut is getting fairly old but it isn't out of the realm of possibility she could live another 5-10ish years. Or at least I hope and pray she could have that many more years in her.