We went to a wedding years ago that started at 7 and finished at 11 and they were literally taking drinks out of your hands to get you out of there and turning the lights up etc. It was quite rude the way it was done so that kinda turned us off and we don't have great memories of that wedding because of it kwim? BUT I think if you made it clear that there will be a finishing time your guests will know what to expect and also those that want to party on can make their own arrangements etc because at the time we had no idea what was going on and it felt odd.