Very good reminder. I got mine out a day before I left for an elk hunt this year and tried to send a test message to my wife... no go. I could send messages to her email address and to other buddies, but messages to her phone and my phone would not go through. Evidently it had something to do with T-Mobile blocking the messages as spam, because the messages contained a link. Not a life and death situation as I could still use it to message and I'm assuming the SOS function would have worked, but a good reminder to test things out well in advance of leaving. In the end I changed a few settings and was able to get it to work, but wasted quite a bit of time messing with it when I should have been packing.
And yes, I did have to do a software update as well.