Out of curiosity how often do you tweak the time decay of a given post? Also do some posts have different time decays based on the content (eg. Who's Hiring? vs YC job post vs standard post)?
Yes: job ads have their own time decay algorithm that starts them out at #6 or so and steadily lowers them over about 3 hours. There are other switches that cause some posts (e.g. stories without URLs) to decline faster, but I think they all work on other variables than time.