premise: Emperor is a Norwegian black metal band formed in 1991, regarded as highly influential by critics and emerging black metal bands. The group split up in 2001, but reunited from 2005 to 2007 for a few festival dates and brief US tours, and again reunited in 2013 to 2014. The group was founded by Ihsahn (guitar/vocal) and Samoth (then, drums).
hypothesis: Emperor originally played together for 10 years before first splitting up.
reason: It is definitely correct because it states that the band was formed in 1991 and split up in 2001 (10 years). I think my wording may have fooled the model.