Generally i go w the guideline, 60 min or longer of playing time, intermission ie 10 min, people get up stretch walk around, talk, restroom water , etc
,house lights on.
less.than 60 i have used an interval, 5 minutes , houselights if turned on are dimmed, and people can talk stand up but not long enough as intermission, just a quick breather for you. Interval would be more for you than audience.
