I will fly singles over the top or IFR in IMC, if I feel the ceiling is high enough such that if the fan stopped, I would have enough time/room/hospitable terrain so as to give me a reasonable hope of making a survivable forced landing. That being said I much prefer flying a twin in these conditions. What I will no longer do under any circumstances is fly single engine aircraft at night. You can joke about turning the landing light on if you do not like what you see, but the reality is finding a survivable place to plop down after an engine failure is too dependant on luck for me. BTW the latest statistics from the USA show that you are 20 times more likely to kill yourself in a single engine aircraft (on a per hour flown basis) at night than during the day