Service pack 3 of release 11.7 shipped in May of 2018, almost five years ago. You should update to 11.7.17; there is no cost other than your time.
The maximum size of a data extent is 2 GB when the large file support feature is not enabled, and 1 TB when it is enabled. Prior to 12.0, large file support was only available with the Enterprise RDBMS license. This feature should be enabled in all databases where it is possible to do so.
My personal comfort zone for extent size is to keep them to at most a double-digit number of GB, say 20 to 50. Other people may have different preferences, given their experiences and the size of the databases they work with.