Sometime in the second millennium, Realistic manufactured a Chronomatic radio alarm clock, which my parents bought for me. Over 2 decades of use later, my reliable alarm clock had only started dying. It had lost its radio capability, but it could still be set to beep loud enough to wake up an entire room, no matter its size. Unfortunately, if the volume control could possibly set the alarm's sound in the past, that feature had broken long ago, so when I realized the prospect of being awakened by such a heart-threatening sound had perhaps become scary enough to make me lose sleep, I decided my oldest electrical device had earned the right to its ultimate sleep, while I had earned the right to buy a new, smooth alarm clock.
After a careful on-line search, I decided the Chronomatic's successor would be a Timex T128BC3, sold by Walmart for 25 CAD, part of Timex's T128 series. While this remains a fairly cheap device, after a few weeks of usage, I can say this purchase will have been worth it if the clock is still working as well in 20 years. The alarm can be set to be gradual, very smooth. The display is OK. The battery-based Sure-Alarm feature is well-designed, although it's disappointing to be unable to see the time when the power is out (there is no button to display temporarily). The nap feature is nice.
The weaknesses I found are:
Update 1: A few months after replacing my Chronomatic, I was shocked to notice that a woman my age was using the same alarm clock as I did. Hers had only started dying too. Wow, these Chronomatic clocks sure stand the test of time!
2018-10-13 Update: For the first time, I was awakened by a Sure Alarm during a power outage this week. I did not manage to stop the alarm without removing the battery, which is non-trivial (supposedly requires a tool, although I managed without). Either the button feedback issue combined with the lack of light and my lack of sleep that night explains my inability, or the clock failed to disable the alarm. I will try to update this next time Sure Alarm triggers.