in my opinion you will only get banned if you get reported by other players, i dont think they can detect the bot by itself
and you shouldnt bot 18 hours a day.. it is too obvious for blizzard. an account which plays 18 hours a day, it has to be a bot or somebody else is also playing on that acc which means acc sharring and i dont think that this is allowed
blizzard is banning in banwaves every few weeks, they dont ban the botters on the same day they detected them. your acc might be gone with the next banwave, if you're lucky maybe not
this is just my opinion
(i'm a long time botter here)