Personally, I love the shyt. I'm not expecting a flash of lyrical prowess when I listen to these boys, I'm expecting gritty rhymes over hard hitting trap beats, and a boost in social invincibility when I listen to them, and I get just that.
"Traffic" my 2nd most played song on iTunes, and is the most played song on my phone. A nikka feels untouchable listening to that shyt around school.
I think it's silly for others to place an age limit on listeners of this type of music. Everyone is built differently.