Yep, could always rely on the Shackleton to arrive several hours after the party was over.
Not always!
We were once keeping an eye on a brace of Bears, which left the area of interest to the south-west and descended to low level....
Some hours later, a Shacklebomber picked up a contact well to the west heading north, which hadn't been seen by the concrete cave-dwellers. The vector which was called by the Shacklebomber team resulted in a successful intercept, which turned out to be one of the previous Bears on its way back to Mother Russia.
Without the Shack., we wouldn't have been able to make a successful intercept as the geometry which would have resulted from an SOC contact would have yielded a lengthy stern chase and the Sovs would have been well out of the area of interest before we could have nabbed them.