Once I have unlocked the SIM slot on my Incr2, do I have to unlock it again each time I put in a new SIM?

[irmo123]

I used my phone a year ago in Spain by locking the SIM slot and purchasing a local SIM.  Once I returned home I put my Verizon SIM back in.  I'm going on another trip, do I need to get the unlock code again or is the phone now permanently unlocked?  I'm hoping I just need to power down, put in the new (temp) SIM and power back up.