A few minutes is more than enough under normal conditions. Modern electronics all have bleed resistors that drain any dangerous capacitors when the device is of

A few minutes is more than enough under normal conditions. Modern electronics all have bleed resistors that drain any dangerous capacitors when the device is off. In microwave capacitors the bleed resistor is built into the metal can of the capacitor itself. You should always assume capacitors are charged unless proven otherwise. Just grab a screwdriver with an insulated handle and short out the capacitor before assuming it's safe.