What would be the average runtime on high (350-400 lumens), from a Cree XP-G2, 2.8-6v, P60 drop-in on Cr123 primaries? I think it draws 1.4a at the tail.
Based on discharge curves of CR123 batteries, my guess is 35 to 45 minutes depending on how the driver is implemented and on the discharge characteristics of the batteries (some differences between brands).
It also depends what you intend by runtime - i.e. down to 50% or down to 10%. Some XP-G2 lights on the market get close to 1 hour and half on CR123s but it's down to 10%.