I'm using a Motorola Defy from 2011. The thing runs Android 4.4.4, gets about 4-5 days / 7 hours of screen time on a single charge. It does not get slower 'as every Android' which is not that surprising given that Android itself is not susceptible to slow-downs like e.g. Windows is. I'm careful not to heap too many background-active apps on the thing to keep it nimble. I don't use live wallpapers, widgets or other such trickery. I also try to keep storage (internal and external) from filling up as those do get slower the closer they are to full.
I enable mobile data when needed, i.e. when out of Wifi-reach. I also use the phone as wireless access point on those occasions when the - rather spotty - ADSL connection has given the ghost.
