I have an Arc-AAA modded by LedASAP. On an alkaline cell it drops very gradually. It reaches 50% in about 5 hours (same as the unmodded light). On a lithium cell the runtime is slightly longer to 50%, but the brightness drop is negligible (behaves almost like a regulated light) for a long time. This is from memory -- I ran these tests a couple of years back.
That sounds about right. As for the lithium AAA cell (which is a PRIMARY cell, made by Energizer for folks who might not know about these), the discharge curve is pretty flat, like Rudi said... think of it as a kind of poor man's regulation!
Also, for CPF young'uns, back in the day LED_ASAP was basically the king of tiny Luxeon mods... he worked his magic on a number of ArcAAA hosts and if memory serves, also some ArcAA and maybe other similar-sized lights. His work was top-notch... he had a real talent with those tiny bodies. Skalo's light is a piece of LED history, CPF history, example of some pretty fine workmanship by a great old-school modder, and the icing on the cake... it's still a darned usable light even in this day of uber-bright Seoul and Cree and Rebel! For the asking price, I'd imagine somebody is going to be very happy.
Oh yeah, bump for a crazy seller and all-around great guy! :thumbsup: