Give the bombers a target worth hitting that will stay down longer than the trip home.
Sounds good.
That 6 hour destruction duration for strats I'd be against.
A 90 min to 2 hour window I'd think passable.
Imagine a 6 hour window: Fester & Friends pork ammo factory at 3PM. So for 6 hours through prime-time some woebegone country's bomb production is nixed. No, says I.