I've found that this capability is not working as it should for PGA golf.
When I DVR the PGA on Thursday and Friday on golf channel it adds 90 minutes to the recording even though on those days the broadcast always ends on time.
On Sundays, for the CBS broadcast, when there could be a playoff or a weather delay auto extend is not happening. It hasn't happened the last two weeks when the broadcast ran over.
What's even worse is that prior to X1 it was easy to manually extend the recording when you set it up. I recall you could add up to 2 hours. Now the options are 3 minutes or 5 minutes, basically useless for sports. Either fix the auto extend so that it actually works or allow easy extension during program setup.
Great post and I feel your pain. Over the weekend I recorded a baseball game and the recording did not extend at all. Cut off after 3 hours. The feature needs to be fixed or completely removed. One or the other. Very, very poor service to offer this feature and it's not working, huh?