Some facilities, based on their written procedures use the same posted form for multiple consecutive shifts/days. You still need to do all the prescribed safety checks on a regular basis and have it reflected on the permit. It just saves on having to fill out a new form for each day/shift. The form will need to be big enough to reflect entrants, watchers, gas testing, etc.
"The duration of the permit may not exceed the time required to complete the assigned task or job identified on the permit in accordance with paragraph (f)(2) of this section."
The permit can remain open as long as the crew or at least the hole watch is there. If everyone leaves for lunch, you should really renew the permit because without constant monitoring, conditions could change and the confined space could become deadly for an entrant.
