Do you do much to keep them supple (or, alternatively, too much)?
Could be worth persevering with the exercises as it may take a while to feel the benefit. Much of what physio does is giving you exercises, in my experience anyway.
Massage could also help, by a proper practitioner. I find osteopathy helped by back a lot, getting it freed up then trying to keep it that way and I always got lots of advice of them as to other things I could do to help such as exercises and posture.
The work must go into not just getting it feeling better but keeping it that way.
I have had to look at my posture generally as I had a tendency to spend a lot of time hunched over a computer or papers which used to kill my back.
My osteo asked me to move my arms about as much as I could in my usual posture then to sit or stand up straight, shoulders back etc... and try again, the difference is pretty telling.
Maybe swimming, yoga, pilates etc... to keep yourself supple and improve your posture? My rhumatology nurse recommends all these for my arthritis so I'd say they have a good chance of also helping generally stiff and achey joints.