If you use the createHlsStream API command of the EMS, you can set its parameters as follows:
1) playlistType to "rolling" (the default is "appending")
2) playlistLength to the number of chunks to keep playable (the default is 10)
3) chunkLength to the duration of each chunk in seconds (the default is 10)
You would then be able to playback playlistLength x chunkLength (in seconds) relative to real-time. The default only keeps 10 x 10 seconds (less than 2 minutes) of history.