Disco didn't come and go as rapidly as across three years. I talk in much more detail about the genesis of disco in this comment here, and identify the beginnings of disco as a chart-topping sensation as a style that was identifiably a new dance music style in 1973 (with earlier precursors from the previous five years or so), and which was noticeably a style having big hits in the US by 1974 (e.g., 'T.S.O.P' by M.F.S.B. or 'Dancing Machine' by the Jackson 5). In another, earlier answer, amongst other things, I talk about the huge amount of disco hits on the charts in 1979. So that's more like six years of disco hits, which is more or less about the same amount of time that grunge lasted in the charts, and comfortably beats out dubstep. Later on in that answer, I also discuss the process that led to less disco songs on the charts, what happened after disco, and the way that the style mutated in the dance music underground into styles like house with deep roots in disco.