I don't (unless I break or lose phone). I try to keep using the same computer/phone/gadget for 3-4 years to get my money worth these days.

I just feel like it's a rip off to ask me to shell out £500 every two years for new iPhone, £600 for new iPad and £2000 for new MacBook Pro (prices are my best guess, I think new iPhones actually go for as much as £700 with better specs). So I try to go using my current tech longer.

It's also environment friendly. Bad for companies if more customers start thinking like this because they depend on selling the same device over and over again with minor tweaks.