I have my iPhone 5s since it came out almost 3,5 years ago. It still functions great! The battery life is still very decent after 3,5 years so a new one should be even better. I commute every day for 2 hours (1 to the city and 1 back), while using 3G (surfing & chatting & listening music - all at the same time) and I always make it with my battery life till I'm home at 17:00.
I think, however, that the iPhone SE is a better deal as it has (way) better internals. It has the internals of an iPhone 6s (flagship of last year), which means faster chip, better camera, better screen. If you have some more dollars to spare the iPhone SE comes in at $399 for 32Gb sim-unlocked.