sleep time accuracy

I’m after opinions on the accuracy of the sleep times. The scenario is that Xbees can sync at startup but they may move out of range for days at a time. So I want set sleep and wake times that guarantee they re-sync when they come back in range.

For example.
If I set
non sleep controllers to sleep 4 seconds, wake 1 second.
sleep controller to sleep 1800s wake 10 seconds

when the non sleep controllers sync they will be on 1800s/10s.

If they dissappear for 72 hours will they still be able to sync with others?

I can’t find anything in the manual to give me confidence it will.

What is a nice feature is that if I power cycle the non sleep controllers they will revert to their original 4s/1s cycle. This is handy for re-synching with the sleep controller.

Opinions please. Anyone have any real work/ measure experience on this?