Will Key fob still work if I take out battery, and replace when "needed"
 

I guess my question is...if I stick my spare fob in the car and remove the battery, does it ever lose its memory after being stored for that long?

I plan to order a blank emergency key, have it cut to my car, then store it on the car in case of an emergency "lost my key" situation.

If I hide my spare fob under the dash somewhere with a spare battery will it work instantly, years from now?