To date, 434 episodes of the series have aired, enough TV to fuel a 13-day binge-watching session — without ads. Excessive? Maybe, though anyone who’s fallen under the spell of an “SVU” marathon on cable, where reruns are nearly ubiquitous, can attest to its compulsive watchability. To hear that signature “dun-dun” — or “chung-chung,” depending on who you ask — is to be instantly hooked. In the 2017-18 TV season, viewers spent 135 billion minutes watching “SVU” on NBC, USA and Ion, according to NBC.