If you’re familiar with the BLF A6, the Astrolux C8 has the same performance and drain characteristics. Max drain depends on what your cell can deliver, but a rough ballpark is about 5 amps when fully charged. This drops as the battery depletes, due to the FET driver. On medium and lower modes, the 7135 chip uses a constant draw (for example, 350mA on the middle mode).
Due to the 45-second step-down to the second highest mode (which will either be level 6 in the 7-group mode, or level 3 in the 4-group mode), you’ll get decent run times of about an hour or more. But if you run it on max the whole time (definitely not recommended for more than about 3-minutes at a time), it will be about 30 minutes until you’ll want to change the battery. It takes a long time to drain completely, as it will drop output as the cell drops below about 3.0v. IIRC, it doesn’t shut off completely until 2.7v or 2.8v. But, yeah, for a thrower, moonlight mode on a depleted cell isn’t much use.
If you want longer run-times, the Convoy C8 makes more sense. It’s slightly better regulated, and is more efficient than a FET driver. And, of course, it has lower output which certainly plays a big part in run time.
On medium and lower modes, the Astrolux uses its 7135 driver, so performance is identical to the Convoy. Though, the Convoy’s medium brightness is about half the output (and current) of the Astrolux, so you can’t really compare them at the same output level.
Yeah, I know, it’s not much help. But FET-driven lights are really hard to quantify exactly.