Definitely slows down over time. This is a combination of two things: 1) Android was not very optimized for smoothness before 4.1 Also Android updates in gen

Definitely slows down over time. This is a combination of two things: 1) Android was not very optimized for smoothness before 4.1 Also Android updates in general have addressed a lot of performance issues (TRIM in 4.3 was a big one). 2) Apps are generally coded to harness the power of modern devices. In Android the difference in power between today's devices (Quad Core 2.0Ghz) and the devices of yesteryear (Single Core 1Ghz) are massive.