The one second per hour was a quicky guesstimate on my part.
10 characters @ 2400 baud once per hour is more like the real situation. Add that to some RF data-slicer set up time and the real amount would probably be more like 62ms (just a tad bit different from the one second I originally planned!).
But the math...does it sound right, feel right? Theoretically of course...
I don't really expect a coin cell to run for 2 years with my building ability...2-3-4 months would be just fine with me.
JDG