Low Battery Warning?

Does anyone have any real life experience yet of when the low battery warning kicks in? I know on my original Varia RRL it gave the warning about 5-10 minutes before it died, which was no use whatsoever. Ideally I'd like to be able to set warning thresholds like you can on many Garmin watches so I could set an alert for 1hr remaining which would generally be enough to let me know that I needed to charge once I got home ready for my next regular ride.

However, failing that I'd just like to know that I'd got enough time to turn round and head for home if necessary.