I don't know how *Linux* uses the term, "supported till a certain date" since I'm using 'Live' CDs. I do have some experience using old, sometimes very old, CDs of Linux iso images. If the CD works 'Live' on your hardware, it will keep on working and the worst you get is, for example, in a Puppy log-in where the default browser is an old version of 'IceWeasel', is a screen with, "Oops, URL not found", which you can just ignore.
Upgrading within a version in Mint could not be easier. At the top bar there is a 'shield' shaped icon with, "i" in it. Mine currently shows, "9 recommended updates available (39MB)". If you open this your system will be checked and the updates will be listed with check boxes and 'rating' numbers ( 1 - 5 ) beside items. "1" is highly recommended and *very* safe. I chose not to upgrade Firefox from v11 to v12 by unchecking the checkbox. You can do the same for upgrades numbered 4 or 5 if they are not important to you since there is a small chance, according to what I read, they might interfere with some other files. In Mint 'Applications> Other> Upgrade to DVD edition' you are given the opportunity to upgrade and I think you have choices. There is 'Applications> Other> Update Manager' that I've not explored, along with Synaptic Package Manager and GDebi Package Installer. I believe the same process works on an install to CD-RW (probably not big enough), DVD-RW or USB flash drive.
I've read about version upgrades and will review my notes and let you know.
@dantheman Re. today at 01:26:32 "...LXDE for a spin..."
Great. You are welcome.