In England it costs you £20 and takes 20 days to unlock a phone. I tried to use my iP5 with a French sim and was horrified to see that it was locked (to T mobile) and I had no idea. I tried the same Sim on my old iP4 which is now under an orange contract and same thing, locked. Same cost and time frame to have it unlocked. I had to spend hours on the phone to Orange, T mobile and Apple to find out.
The iP5S I'm getting - when they decide to make the gold models available to meet my order - should be unlocked because it will be sold by Apple itself. I shall definitely check it.
Rant over
I'll confirm this as being incorrect. Once an iPhone is flagged in the system to be unlocked, it is in fact, unlocked. The system is not relocking devices after a short period.