Running the bike completely empty can and will damage the bike. The fuel pump uses fuel running through it to cool and lubricate the motor and rotor mechanism. Allowing the pump to pick up air can cause it to over heat and wear out sooner as it surges trying to maintain the pressure with air in the system. If it happens, there's nothing you can do about it. But it shouldn't be a habit of running it the the absolute mileage limit before refilling. And that mileage will vary greatly based on how you ride the bike, how much you filled it up with fuel, and each bike is slightly different.
Log the miles on the trip meter. When the light comes on, you have about 15-20 miles to find a refill location. For me that's around the 110-115 mile mark on the trip meter.
I end up "pushing" every bike I've owned to well beyond the reasonable limit to see just how far I can go.
But let me be clear about what I did; I was basing my risk on actual fuel used, calculated using the bike's onboard fuel flow metering, not mileage. Mileage alone is of course a highly inaccurate way to determine range as it can vary. I have found the Gen 4's fuel flow meter to be very accurate over the last 5000 miles or so.
This was a calculated risk; I did the same with my other bikes and stretched it right out to the last mile, never ran out. I was using strictly the mileage to calculate the range on "fuel light flashing". On this little sojourn I had reset the average mileage twice to figure out how far I could get on what "should have been" remaining in the tank. According to the specs and my calculations based on the data, this definitely should not have happened.
I was getting 39 mpg at speed over about a 100 mile run, mostly in 2nd gear. I reset the average mpg once I got back to the slab, and was seeing 43 mph average.
When I left the house, I was showing 3.5 gallons used from the last fillup. Thus I calculated I could go another 30 miles comfortably given a usable capacity of 4.5 gallons.
I started getting nervous when I saw "4.0 gallons" used about 10 miles from my destination so took an alternate route with a closer fuel stop. Good thing I did that or I'd had a much longer day of it getting fuel (I have Auto Club m/c and RV coverage but what a pain in 105 degree heat, right?).
When it ran out, idling at a stoplight, the meter still showed 4.0 gallons used, and as I recall, just over 160 miles traveled.
As I mentioned, the tank took 4.07 gallons to the neck, topped up.
So it ran out at a point where I thought I would have at least a liter or so left, surprise, surprise!
Regardless of what they say, the actual tank usable volume is less. I was able to stretch my F800GS out to the limit and got nervous but didn't run out, over 200 miles and low fuel warning in my face for 40 miles (plenty of gas stations around).
I was thinking about scout saying he'd run out a couple of times, now I see it's not uncommon.
Of course I'd never have tried that in an airplane, or if I was traveling far from help, lol