How long does $5 soldering irons(that plug directly into mains) last?

I'd recommend one of these

https://xtronicusa.com/Stand-Alone-Soldering-Stations-c11945097

I have one of the 4000 series combo hot air/soldering iron stations, it has performed very well for assembling a Lot of boards since 2011. And the occasional rework of SMD parts when reflow didn't go that well.