watching recording before it is finished

yesterday I tried using the DVR for the first time.

as expected the DVR was about 2 hours into a 5 hour recording. following my habit from Windows Media center, I started watching the recording. this way I can skip commercials and eventually catch up the live broadcast.

BUT, when I got to 1:47:00, I found to my horror that the recording had stopped.
AND the broadcast had ended - couldn’t even watch the end of the event.

  1. is it possible to set an extended ending to the recording? many sporting events continue past their scheduled ending.
    2a) why did the recording stop?
    2b) do I have to wait for Plex to finish recording before watching the recording?

would prefer to use Plex but am also reinstalling Windows Media Center as a backup in case of future hiccups.