Rebooting routers and modems - How long?

[#1]

If you're asked to reboot a router and modem by tech support is there a recommended time to wait before powering them up again. I've seen requests that just say reboot and others that say wait 30 minutes before powering up.
Thanks

[#2]

Depends on the reason, if for a settings change on PN side, wait 10mins for it to filter through and then just do a reboot.  If its the exchange not seeing a disconnection and you can't get a connection after it, power off or disconnect the router from the socket for 30mins for the exchange to kick in and see it then start it again.

[#3]

Like Gus says, it depends on the reason.
I would always go for a quick restart first (ie turn off and on again), but on some occasions (exchange maintenance being one) there can be something called a stale session which requires you to turn off for an hour before retrying.

[#4]

Gus & James, Thanks for that info. it makes more sense now.