I know it depends to a great extant on what type of enviro you are operating in.  But ON AVERAGE how far will different lumen levels allow you to fire at night?  I know that these are rules of thumb.  

For instance, how much light do you need to illum to 50 and 100 yards?   How far out can you go?

A good general rule of thumb is 1 yard for every 2 lumens, i.e., 100 lumens sees 50 yards.  This guesstimate will give a good level of pretty strong light.

There is no rule of thumb.  Lumens cannot predict distance AT ALL.  Its like asking how much powder do you need to shoot a bullet at a certain distance distance.  Reflector size, beam shape etc come into play.

New AR_Guy is also telling you the ABSOLUTE MAX for Surefire P60 bulbs (65 lumens) in a 1.47" bezzel like the Millenium series has and MN10 bulb (125 lumens) in a 1.62" bezel.  A 120 lumen P61 bulb in a 1.47" bezel will NOT reach 100 yards at all. LED also has nothing to do with throw.  A G2 has the same throw as an X200A for example.

Let us consider SureFire's lights first.

The P60 (65Lu) and the P61 (120Lu) use the same diameter reflector.
There may be twice as much light output but it does not create a beam that is twice as intense.
The extra light output creates a larger beam.
The P61 does not increase the range significantly. However, it does allow you to see more at the same range, more clearly.

The same is true for the rest of the high output lamps.

If you increase the diameter and/or depth of the reflector the light can be focused into a more intense beam that can be used for illuminating targets further away. An example of  this is the M3 and the M3T.
The TurboHead of the M3T is 2.5" diameter and creates a more intense beam compared to the M3 as a result.

It should also be considered that the beam from one reflector can be designed to be very different from another of similar dimensions. For example, Pelican, ASP & TACM tend for thinner, more intense beams, and Pila tend for wider beams.

So it is very difficult to predict beam shape (and from that beam throw) from a Lumen rating unless you know a lot more about the product.

With regards to LED beams - they tend to become 'washed out' by ambient lighting (especially street lamps etc). The effective range of an LED beam is often seen to be reduced outside. Also, because white LED light is not "full spectrum" (it has pretty much no red light) the clarity of the illumination at distance is not as good as with incandescent light. Some people report that white LED light can become difficult to see by in green vegetation.

I read that at least 60-65 Lumens is needed for target illumination and recognition within handgun range, and at least 100-200 Lumens is needed for target illumination and recognition within rifle/carbine range. In most cases the reflector diameter and depth will have to increase too.

Al

I still dont buy the LED is harder to see thing.  Using LEDs right next to incandesant bulbs I see the same distance with either when its low output up to midrange when they are both well focused.  I cant seem to find equivalent lights that wont let me see the same distance.  All the LEDs with less throw I can find are due to the beam pattern being broad.  Perhaps I have weird eyes.

I don't tend to see very well things at distance in low light.
People on CPF tend to say they see differences in beam throw that I can not see.

It's important to note the people see differently and that some experimentation with different types of light may be required to find the most useful beam for you.

I use the SureFire L2 as my everyday light but when I go outside at night I switch to a incandescent such as the M3T, M6 or 10X.

Al

The 125 lumen MN10 bulb assembly in my 9V M962 does a fair job lighting up skunks in the garden out to 100 meters or so. If I ever had to identify a person at that distance I'd opt for a turbohead with the brighter MN11 bulb assembly (or step up to a bigger light).