Maintenance windows may be scheduled for weekends, when the site may be unavailable for anything between 5 mins and 3 hours depending on the scale of work.
Advance notice of maintenance windows longer than 10m will be given via your dashboard (what you see after logging in).
If you are unfortunately working in the system when we begin a maintenance window, we cannot be held responsible for any lost work. (Though we'll consider any fair claims to replace the mug of tea you threw against the wall.)