I still use the 5. It's still a good phone. But mine needs a new battery. The 5 is getting old now. But if the battery is good, and the buttons hold up, it should last at least another 2 years.
The iPhone 5 is almost three years old. It really depends on the condition of the device. Me personally, would go no later than an iPhone 5s as my first iPhone, but thats just me and my preference.