When exploring the wasteland, there are special events that trigger at or around 60 hours of exploration. Is it possible to recall someone who has been exploring 61 hours and triggered the event and then tell them to resume exploring once they've walked an hour home to trigger the event again? The hour walk home will have set their exploration timer to 59 hours, so will they find the event the second time their timer is at 60 hours?
Updated answer for 1.2+
With the latest update, recalling a dweller from the wasteland does NOT count down your explore timer. If you were at 60 hour, recall him for 8 hours, and then set him to explore again, he will resume exploring at the initial time.
This also means if you then recall again, his return trip is reset and you have to start again at
Explore Time / 2.
I can't certify this for all major events, but for the 60th hour National Guard Depot, I can confirm that you must return to the vault to trigger it again. I ran my dweller up to 61 hours (measly 125 xp from the National Guard, no weapon), then back to 58, and upon hitting 60 again it triggered a "standard" event of finding something in the wasteland. Therefore I conclude that you must return to the vault in order to be able to trigger the National Guard again.
No, it's not possible. If you recall a dweller from say 61 to 58 hours, and then set him to explore again, nothing will happen until he's at 61+