My F103 powers itself on and sometimes get stuck. It went for months without doing that but then it started up again a couple months ago.
If I won't be home, I disable the inactivity setting. When I'm home I just press a button when programming starts. I suppose the clear button would work to reset the inactivity, but I seem to catch the commercials, so I press info to get a record of the program info. Worst case is it's on longer than needed, 6 watts an hour. If I'm around when programming is done, I shut off manually.
The guide info doesn't work all that well for me, anyway. A couple stations report 6-7 days out, and others report stuff like "paid programming" as separate half hour programs, so it dumps info it already has, trying to get more. I can't even count on 12 hours for every station, but it does fill in programming if I tune to a station for 15 minutes or so. I think it's supposed to dump past guide info in standby, but it seems to dump future events, too.