Self-contained and central battery emergency escape lighting should have 3 hours' autonomy (BS EN 1838 and BS 5266); theatre operating lamp inverters at least 3 hours (BS 7671). Fire alarm and detection batteries should meet BS 5839-1 (24 hours quiescent then 30 minutes in alarm), with about 100 hours worth considering for premises closed over long weekends, independent of any secondary supply.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.