I find when I'm leaving the house to go into the yard, or basically if I'm not in close vicinity to the router the 5ghz channel switches over to 2.4, & the switchover takes a few moments and it's just annoying. My devices don't perform any quicker on 5 GHz than they do on 2.4 GHz ( which is possibly due to them being older for the most part), so there's no need for me to use the former over the latter.
with my Ac66u, the 2.4 & 5Ghz bands are displayed as separate wireless channels (Asus 2.4G & Asus 5G), each to be connected to when needed/required, by removing the 5Ghz option, i have also removed the time it takes to switch between the 2. And, as i mentioned, there is no speed benefit over 2.4G even if im 3 feet away from the router, so enabling it is useless in my case.