Are discretionary background URL sessions guaranteed to run?

If the app schedules a a discretionay background URL session for some point in the future, is the OS actually going to run it? Even if the app gets terminated before will the OS launch the app in the background? Or does the OS only scheudle the url session based on app usages patters? - i.e. suppose the app schedules a background URL session with a lengthy earliest begin date of something a month, but then if the user doesn't actually interact with the app much if at all during that period, will the OS not bother to schedule the session because the user didn't use the app much? (similar to current background schedulding, where the OS doesn't schedule the app at all if the user doesn't use it).