First question is pretty basic and that's why is high-volume website being taken down during the normal business hours not once but twice - instead of having maintenance run in the early morning hours (granted that's the middle of the day for some timezones, but the US is where the majority of the FT volume comes from)

Second is WHAT changes are being implemented? Excuse me for being blunt, but past "maintenance fixes" have hurt not helped this site on multiple occasions, so what is being changed by the work?