I want to disable a link on a cisco router but have it enable again automatically after a certain time, if i lose connectivity - is this possible to do?
A very crude way to do this would be to save the running configuration, make the change and then set the router to reboot.* Many engineers use this method when working remotely to ensure that they can get back to the box is they accidentally break the way they're connected.
Use the following command to set a reboot in 5 minutes (I don't know what the max is, but it's always in minutes). And then use the second command to subsequently cancel it when you're happy.
Don't forget to save the running configuration when you're finished, if required.
*Edit: I've just re read your post and actually, I think you're doing exactly what I described in which case this is accepted practice and not crude as I initially posted. What would be crude (IMO) is using this as a way to automatically revert configuration in a weeks time or something!
You can use the command scheduler in Cisco, KRON, to execute commands at certain given times.
Docs are on Ciscos website docs.
If you wish to run an interface shutdown / config change / no interface shutdown at the same time you can easily execute a stack of commands in a TCL script on the router without having to schedule or do anything special.