Blackburn claims a run time of five hours in the manual for the System X3, and the outside of the box has a graphic showing a run time of four hours. But ours fell 49 minutes (or 1hr 49mins) short after conditioning the battery (we never test run times on a brand new battery).
Prior to and following the actual test we achieved, on average, run times of around three hours on full power. It's not a bad light; not that bright but with a good beam spread and excellent build quality.
You also get an easy to use mounting that's simple to remove without tools - which is handy for commuting. The cable connections are flimsy plastic that are easy to cross-thread, but they seal well if you take care. The battery is designed to fit into a bottle cage (or just to a frame tube), but we only found one cage it fitted into in a reassuring manner.
The wide velcro strap on the pack is good though, offering plenty of security and ease of use with gloved hands, but it isn't removable from the pack. The battery indicator on the battery pack changes colour from green to red to show the level of battery charge, but it can vary depending upon external temperature, once turning red only 20 minutes into a ride though the light was fine and bright for a good two hours after that.