On the Media Center it really depends on how the padding is setup. If you setup the "Stop later" option under advanced record (or the series record screen) it is what's called "Hard Padding" that will applied no matter what, and this can cause conflicts with any shows scheduled afterwards.
The other option is to use "Soft Padding" which will extend the recording up to the time set if there is a tuner available, so in the above example it wouldn't extend as it would cause a conflict. By default Media Center can only be set to 4 minutes of pre and post soft padding, but by using the IceTV Interactive software you can set this to have a higher (anything up to 60 minutes) amount of soft padding.