Daily
Radiator hoses and heater hoses should be inspected yearly and replaced when neccessary.
before use
For fish tanks, weekly, at a minimum.
The whole vehicle should have a safety inspection every service.
Fire extinguishers should be inspected annually - by a suitably qualified person.
The error rate is less taht 1%. You should have your valves inspected often.
The contents of any emergency kit should be routinely inspected, depending on the anticipated necessity and/or the current disaster "season." Depending on where you are, it should be inspected and replenished every 6-15 months, if not more frequently.
They are inspected at least once a year. Inspections are random - and without warning.
About maybe twice a year
before and after
about twice a year
Once a week. Change water every 2-3 weeks. Keep it clean though.