I recently bought 5 12V ultra bright LEDs (all identical), and want to hook them up to a battery pack of 8 AA batteries. So I figured I could just make five parallel circuits with one LED in each, and hook them all up to the 12V DC. Since I'm quite new to hobby-electronics, I'd like to hear your input.
1) First of all, I've read in a related question that it's a good idea to always have a resistor in such circuits, even if the voltage matches the LED exactly. How many ohm should this resistor be?
2) It's ok to put the resistor "before/after" the the 5x parallel circuit, right? Or should I have 1/5 the resistance in five resistors, one in each parallel circuit?
3) Since the circuit now has a resistor, and it works by generating heat by consuming power, won't the battery be drained quicker with such a resistor in the circuit?
4) Finally, are all "regular" LEDs 20mA?