When I bought my '05 coupe last year in June, I received two fobs. I took the one in nicer shape to be my everyday and kept the spare in the house. Sometime between June and November when I put it away I had to put new batteries in my daily fob.
Yesterday, after the car being in storage for 4 months I went to use the daily fob and it was dead. The spare - with the old (original?) batteries is still working. What's up with that?

 

Not sure but can say that I had the same issue when I took the cover off of the Crossfire and tryed to use the fob on Sat

 

You didn't say where you stored the key, but I have heard that it talks electronically to the ignition so if it was near the column, it may have drained itself communicating.

 

I have the same situation, I too purchased a 05 limited coupe, last summer.
I recieved two key fobs as well. My car also, has been stored most of the winter, had it out three times in the last week, no problems with the key not working.

 

Seems like I read here that if you don't use the fob regularly e.g once a month or so, the car's computer "foregets" the code and has to be programmed again. I rotate use of my fobs for this reason.