Oil leaks of are minor immediate consequence in most radial-engined planes.
No radiator = more oil needed to keep engine cool.
More oil = two sectors.
I'm confused (admittedly I don't know a lot about aircraft piston engines) - are you saying that a radial engine has a relatively larger overall capacity in the oil system than an in-line, because the radial uses oil for cooling, as opposed to just for lubrication, more than the in-line does - and that means there's more oil to leak so it takes longer for it to run out?
I guess I hadn't noticed because the fighters I fly are almost exclusively radials, except for the occasional Spit XVI which we all know doesn't need oil because it's a UFO.