I've used Nair on my belly and chest like twice, last time was last summer. I got chemical burns both times, but I probably left it on too long. I was super smooth, but for now I think I'll stick to my Mangroomer.
I haven't pushed the (time) limits yet but plan to. The drug store I bought it in had a shelf full of various Nair products; most said leave it on for 5 minutes or 6 at the most. The one I chose said 5 minutes or 10 at the most. My choice was made based on the fact most of them were sold as strips, and I wanna treat small areas like at the corners of my mouth. The one I bought is a gel I can fit on anywhere, not just large expanses of skin.
There's gotta be a reason this stuff is a household name, but it's been a total Zero for me. My beard stubble may be heavier than average, but I'm not Guinness Book worthy imo. Next step is to exceed the suggested time limits before I just throw it out ... I have had no skin side effects from staying right at their stated exposure maximums.