I'm retaining a full history from when I started collecting. The first post I have in the live DB is:
Currently the RSS feed only has the 100 most recent posts in it at the time of generation (which is set to the time of the most recent post).
2014-10-10 11:52:00 | showthread.php?p=857694#post857694 | It's the semi major axis in the left panel. ... | showthread.php?t=48602 | Does the System Map show distance from Star? | Beta Discussion Forum
I was initially going to have it scrape every page of post histoy (on a member profile, not the whole forums!) from the old forums, but it would have been a bit of extra work to make it page through, so instead it seeded with just what was on the first page at the time. Each collection run, per forum member it checks, keeps going until it sees a post it has seen before, then stops, but again with the assumption that the first page will contain this. So if a dev goes on a REALLY fast posting spree and/or my collector has sufficient downtime I might miss posts. If that ever does become an issue I'll make it follow the "More Activity" link as needed.