2032 batteries are rated at about 200mAH, that is if you discharge them at a constant rate of 1mA they will last 200 hours (if you are lucky) because 1mA x 200 Hours = 200mAH. If you discharge at 20mA they should last 10 hours because 20mA x 10 Hours = 200mAH but they won't because they are only designed for low current. I think you'd be better of with the low current LED running at 1mA (if it's bright enough). Try a 1k series resistor to run the LED at 1mA. The LED Vf is about 2V and the battery is 3V so you need to drop 1V at 1mA which is 1k.