Alarm clocks are strange little critters. Sometimes they work properly, go off at the correct time and send you on your way. Sometimes they don't, in fact ours didn't in February when we were due to leave on a trip, so it was retired and we pulled out old blue.
Old blue is pretty reliable, it's not electric so it doesn't matter if the electricity goes out. It doesn't have a snooze button, so you have to turn it off when it beeps. We've often wondered how long it would beep if we didn't hear it right away. Well we've partly answered that question. We had it set for 7 am yesterday because we had doctor appointments and we wanted to get up early enough to do our morning walk before we left.
As it turned out we woke up early and were out of the house before 7, no one thought to turn the clock off. We walked for about 40 minutes and when I came back in the house I heard a persistent beep, beep, beep and I realized it was the alarm clock. I hurried in to turn it off. We now know it will keep beeping for at least 30 minutes (it was 10 to 7 when we left the house). So if we try and sleep on it's not going to let us. Good to know.