Funny that; old habits I guess. Have filled based solely on miles traveled for so many years couldn't do it any other way even if I wanted to. Before that with some small peanut tanks and bikes without much instrumentation had two methods, keep track of time and/or unscrew the cap and look down the hole when you think it might be time. Only once did I ever lose a cap while moving.... 
Use miles traveled for fill up on bikes since I can remember. Bikes I have had with gauges usually just used them as a 'suggestion' to fill up. Always use the trip meter & figure fill ups from that. Have ridden into very strong headwinds & gas mileage drops much more than usual as a result so still consider the gauge then since it is there & is slightly more accurate that the inner fairing temp gauge, but not by much.
The "count down" mileage feature is a handy way to find out in a remote rural area you are about to be stranded unless you are near a gas station. It allows time to plan for how long you think your walk will be or guess the liklihood of somebody picking you up being an ax murderer. Have not run out of gas in quite a few years now, & then I called my BSR since that bike was fairly new & I thought "maybe this gauge is accurate since it is new". It wasn't.
Have not removed the cap when riding in even more years. Do recall when tank was more full than expected getting an unexpected gas bath. Caps are a biatch to find when dropped sometimes...l