There are some weeks where the servers are not restarted for a couple of days. However, on most weekdays, they are brought down for restart, update, whatever.
Taken from SoE's Server Status page (they only list the last 10 messages):
Scheduled Downtime 11/29/2005 10:40pm PST.
All US English-Language servers will be coming down at 7:00 am PST on Wednesday, November 30th, 2005 for an update. Downtime is expected to be 1 hour. - The SOE Operations Team
Scheduled Downtime 11/28/2005 10:00pm PST.
All US English-Language servers will be coming down at 7:00 am PST on Tuesday, November 29th, 2005 for an update. Downtime is expected to be 1 hour. - The SOE Operations Team
(My note - Here was the Thanksgiving holiday, which I mentioned in my earlier post that there were no downtimes for 5 straight days.)
Scheduled Downtime 11/22/2005 11:10pm PDT.
All US English-Language servers will be coming down at 7:00 am PST on Tuesday, November 23rd, 2005 for an update. Downtime is expected to be 1 hour. - The SOE Operations Team
Scheduled Downtime 11/21/2005 7:15pm PDT.
All US English-Language servers will be coming down at 7:00 am PST on Tuesday, November 22nd, 2005 for an update. Downtime is expected to be 1 hour. - The SOE Operations Team
Scheduled Downtime 11/20/2005 10:20pm PDT.
All US English-Language servers will be coming down at 7:00 am PST on Monday, November 21st, 2005 for an update. Downtime is expected to be 1 hour. - The SOE Operations Team
(My note - here is the weekend)
Scheduled Downtime 11/17/2005 10:00pm PDT.
All US English-Language servers will be coming down at 7:00 am PST on Friday, November 18th, 2005 for an update. Downtime is expected to be 1 hour. - The SOE Operations Team
Scheduled Downtime 11/16/2005 8:00pm PDT.
All US English-Language servers will be coming down at 7:00 am PST on Thursday, November 17th, 2005 for an update. Downtime is expected to be 1 hour.- The SOE Operations Team
Scheduled Downtime 11/15/2005 9:00pm PDT.
All US English-Language servers will be coming down at 7:00 am PST on Wednesday, November 16th, 2005 for an update. Downtime is expected to be 1 hour.- The SOE Operations Team
Scheduled Downtime 11/14/2005 8:30pm PDT.
All US English-Language servers will be coming down at 7:00 am PST on Tuesday, November 15th, 2005 for an update. Downtime is expected to be 1 hour. - The SOE Operations Team
Scheduled Downtime 11/12/2005 12:15am PDT
All US English-Language servers will be coming down at 7:00 am PST on Monday, November 14th, 2005 for an update. Downtime is expected to be 2 hours. - The SOE Operations Team
Even though the server is normally not down very long, approximately 30 minutes, sometimes less, sometimes more, they are taken down ALMOST every weekday and I believe this is what the OP was asking.