My wife and I have preferred this type of egg timer for some years, and when one of them wears out (gets cracked and foggy in a few years), we look for a new one. Brookstone used to carry them, so we would pick one up on a trip to Portland, Maine, 90 miles from our home in Rockland. Egg timers that depend on time cues, do not allow for variations in heat, number of eggs, etc. The heat-sensitive timer makes it easier to allow for these variations. We are thankful to Amazon for leading us to the Norpro timer on the internet, and we purchased two, which should cover us the rest of our lives, since we just turned 87. JLM II, M.D. (retired)