The sad truth is that the power consumption varies so much depending on the use case that it's not really reasonable (imho) to give any estimate about residual use time.

What can be given - somehow - is the residual battery charge.

Of course it all would be much more simple if the battery had an integrated uC like most laptop batteries do.

P.S.
It's cool to be able to post again without having to worry of giving away something considered confidential.