Sirius stopped his massive purring a few months ago. He used to be a dominant purrer. I would hear him barge into my bedroom, because of his almost threatening purr. It would wake me up.
Now he purrs maybe once every other day, for a short period of time. He still loves the cuddling, he loves placing himself on top of people and let his big body become a viscous mass dripping to all sides. But his magnificent purring days are over.
He also got his first white moustache hair. He started having cranky old man moments too.
His change of behaviour collides with the arrival of two ball-bearing male cats in the neighbourhood.