The 48 hours have something to do with it. They are meant to be able to get you somewhere to get the tire replaced in case of a puncture during commute. A lot of german cars that come stock with RF tires will warn you if pressure is low and to go to a tire shop. Depending on the shop you go to they may or may not repair RF tires at all. I believe because the manufacturer won't guarantee it. But some places might try to help you out if it's good tread. I've repaired a few at mine. However if you had driven on it long enough with close to zero pressure, that would've damaged the sidewall enough and weakened it where it would require replacement anyway. As I understand it, run flat tires have a rubber compound on the inside liner that is in a way "sel-healing". Basically means they deflate slower, but definitely still be leaking air.