Well in the RAF it was used as good houskeeping, a VC10 would be polished up and all the interior redone for a royal flight, afterwards it could be doing freight, so you are keeping the fleet at a standard by doing it… I would imagine the army is the same, they would be painted etc then go back to normal service, but it keeps the fleet at a standard…. either that or they ae using the war reserve, we used to have buildings full of new Landies in Germany that would do a run out every month or so, then go back into storage in case we ever went to war