Powering LED

Thanks.
ANy idea how long this resistor with 9v would power one low voltage LED

Simply look at the datasheet of a 9V alkaline battery on Energizer's website.
If the resistor is 3.3k and the LED is a 1.8V red one then the current with a brand new battery is 2.2mA (fairly dim) and the datasheet says the battery voltage will slowly drop which will dim the LED and it will be extremely dim in about 720 hours (one month).

Thanks very much