The A330MRTT holds about 20 tonnes more fuel than ol' Bubba's paper plane
might, if it ever gets built....
Even at a (very) pessimistic 6.7 tonne per hour, that's 3 hours flight time.
At a pessimistic 480KTAS, that's an increased radius of action in still air of 720 nm - or 1334 km if you prefer.
Quite handy, one might think?