The other day I asked about this in Einstein and the answer they gave me was that when a project is down, it's up to the stats sites to start decaying the RAC number based on the date it was last issued.

I'm asking this because although LHC is down for more than two weeks, my RAC has stayed the same. Is it a bug, or is it on purpose?

It's not a bug, jsut not implemented i think. The RAC is exported along with the time it was calculated, so it shoudl be constantly changing even when a project is up.

IMO the LHC scheduler isn't down, it just has no work so the status display is not completely right in this point.

Scheduler URL is :

[url=http://lhcathome-sched1.cern.ch/scheduler/cgi' target='_blank]http://lhcathome-sched1.cern.ch/scheduler/cgi[/url]

and it reacts like a "normal" scheduler, so maybe the status script uses an outdated scheduler entry.