If you have the new Interactive Media Guide (now in most FiOS areas), the pause buffer is supposed to be 1 hour, but initial reports are that it only does 15-20 minutes and/or it jumps to live when a new program starts. This should be fixed in future updates. I would recommend recording the program if you're worried about losing it. That way you can start from the beginning and fast forward to where you paused it. If you don't record it and it jumps to live, you will be able to rewind it back to where you left it paused (up to 1 hour buffer).

For the skip ahead feature: If you have the new IMG, you can set the skip length to 10 seconds, 30 seconds, 1 minute, or 5 minutes. Go to Menu -> DVR -> Settings -> Skip. You can also for specify the time for Replay (skip back).