We use roll interval, however it is not a fix applicable in all situations, and it is clumsy. For example, if people use size based rolling along with filenames that are named by header variables, they may or may not be open for an arbitrary amount of time.
Closing idle files on a timer seems to me a far more elegant solution than forcing users to guess an arbitrary time after which to roll or to limit open files(which close in order of oldest, even if the oldest is still active)
I don't really think having the extra option hurts so long as documentation is good. I'm setting the default setting to inactive