LXLE receives its updates through the regular repository channels the same as Ubuntu/Lubuntu, what doesn't get updated through synaptic or update manager are any additional programs added to the default installation and or desktop additions to the gui. In other words, the system, programs and security updates can be upgraded using synaptic, apt-get and or the update manager. I don't push additional program or desktop gui changes through the update manager because who wants to get their desktop all setup the way they like with the programs they like only to have the gui changed and additional programs installed because the developer had an update to the iso that was pushed through the channels. I don't know about you but that would piss me off continuously, which is one of the reason with any distro I've ever used, I disable the desktop metapackage immediately. I look at all distro's regardless of what they come with or how they are laid out as the 'base' system from which I'll build or configure the rest the way I like, and I don't want it to change because well some update they pushed screwed with my layout and added extra programs.

In short, if you like your setup and everything is working, cool, all your programs, system and such will be updated through the channels without affecting anything that you have personally done with your system. Each time there is an new LXLE release doesn't mean you have to reinstall so your system is or stays updated, it just means there is another version of lxle out and perhaps there are a few changes but they are usually nothing to do a reinstall over. Keep your current system the way you like and just keep it up to date using the regular channels, If you want to reinstall thats up to you but certainly not necessary.

Its good to note that sweeping changes to lxle only usually appears between LTS release not incremental updates, In otherwords incremental updates may address a few issues and make some small adjustments, but thats it, I usually try to make a post of what those small changes were so if you like you can apply them to your current system if you want.  The only time I would be willing to say that a full reinstall would be warranted is if you were upgrading from one LTS release of lxle to the next, ex from 12.04 to 14.04, then it would probably be a good idea to just back up and reinstall. Other than that, do your thing, don't worry about incremental releases if everything is just like you want. Your good to go, its your machine not mine, keep it like you want. Hope this helps clear up some update confusion.