Well, I just saw this on Android Police:

agujeronegro

Hey, Samsung released July security patch to Samsung Galaxy S4!!! We are talking about April 27 of 2013. That's 4 years and a half! https://www.sammobile.com/firmwares/galaxy-s4/GT-I9505/NEE/d...

My OnePlus One has Android 7.1.2 and August security patch (thanks to Paranoid Android)

Mine is still on stock but maybe now is the time to learn how to flash and all. Would you recommend doing it also in terms of camera and stability or is it rather experimental for testing new Android features / proof of concept etc.?

I keep my device updated thanks to these custom builds. I use them as my daily driver, totally recommended.