I was surprised at Tom specifically suggesting a rolling average (which is in my experience what most time estimates seem to use with it wildly fluctuating until the end) even though I have occasionally experienced time estimates that get more accurate with progress (not just towards the very end). It seems that what's happening there is an extrapolation of how long everything took so far and what "proportion of stuff" has been done so that fluctuations are eventually averaged out — not just the rate of progress in the last few seconds.<br><br>Going by how rare the experiences of that (the time-remaining estimate steadily becoming more accurate) happening was, most people actually seem to use the rolling average. But now when  I think about it, I'd expect the non-rolling average to be both easier to implement and become more accurate with progress, so why does it appear to be used so little?<br><br>(Bearing in mind that the time-remaining-estimate steadily getting more accurate could just have been pure chance and I don't actually know how any of the estimates I saw were implemented.)