So I just upgraded my router to 18.06. I must say, everytime I do this I hesitate and hover the mouse over the "flash" button for quite a while, fearing that I am looking at days of fiddling without internet access... but unrightfully so.
Once again, the upgrade process was completely smooth, my configuration was preserved as expected and everything just worked.
Everytime I deal with openwrt I am blown away by just how awesome it is. Thanks to all the devs who read this, and keep up the great work!