what are the rules for it being juu rather than chuu?
I thought the rule was as follows: Chuu = indicates the continuation of an activity or a time period juu = indicates a space/time period without a break So 営業中 (chuu) indicates the activity of sales continuing. 春休み中 (chuu) indicates the period of time "Spring holiday" 夏休み中 (juu) indicates the entire summer holidays. 世界中 (juu) indicates the entire world so to distinguish between the summer and spring examples above: 春休み中（ちゅう）は旅行に行くつもりです。 夏休み中（じゅう）テレビゲームばかりしていた。 The spring example defines a period of time and allows us to mention activities that will occur in that time etc. The summer example indicates that for the entire period of the summer holidays a single event occured. What's confusing me is that I thought Miki's summer holidays example should be (juu), because of the zutto. perhaps if the emphasis was more on the fact that the entire holiday had been taken up by camping, we could have used juu?