I own a Galaxy S (2.3.5 / GT-I9000 / BVJV3) and use it since two and a half years. I also have bought more recent hardware, like an iPad Mini and a more recent Android tablet, which comparatively are much more reactive.
So I was wondering if the slowness of my device was just a feeling, or if devices actually become less responsive with time ? The phone is always lagging (click sounds always a second behind), running the basic functions of the phone (messages, phone, contacts) always need a good 4 seconds to actually show on screen, returning to the home screen sometimes takes 5 to 10 seconds while it's doing something to the icons. A game like Pudding Monsters is bacically unplayable, but I didn't expect this phone to run recent games.