Setting an asset to maintenance mode and resetting it to normal mode after 6 hours

What I want to achieve is being able to manually switch an asset to "maintenance" mode, ignoring alarms in this mode, being able to manually switch the asset back to "normal" mode and automatically switching back to "normal" mode after max. 6 hours.

Here is how I plan to do this:

• Add a data item on the enterprise "MaintenanceSwitch", I add two actions (one to set MaintenanceSwitch" to 1, one to set it to 0)
• Add a state machine with two states "Normal" and "Maintenance" with two rules based on the value of "MaintenanceSwitch".
• Add a rule that fires whenever an alarm is created and that changes the status of the newly created alarm when the state is "Maintenance".

Questions:

1. Am I on the right track?
2.  The asset can only remain in "Maintenance" status for max. 6 hours. If the user does not reset it to "Normal" (by setting "MaintenanceSwitch" to 0), a timer should do this automatically. How would I setup such a timer?

Geert