I clean the cup every 2 weeks as i do my water change. The body probably once a year if i have time :-)

Couple times a month. Just cleaned the body for the first time in 3 years.

The collection cup (plumbed into home plumbing) and swabbie gets cleaned about once a month. The body and pump get pulled about every six months for a vinegar bath and scrub.

This picture is after 2 weeks of wet skimming with the swabbie operating for one minute every three hours.

http://i251.photobucket.com/albums/g...2/IMG_0251.jpg
http://i251.photobucket.com/albums/g...2/IMG_0254.jpg

I drain the cup about once a week and clean as needed. I have a swabbie on mine as well and overall it does a pretty good job of keeping things in running order.

few points:

• will depend on feeding, heavily fed tank will require more frequent skimmer cleaning
• as someone mentioned before clean skimmer performs better
• average skimmer will extract waste easier from dirtier water, however not so good skimmer will stop skimming earlier then a better one
• go by the air water mixing provided by the OEM; the more L of air per hour the better. Obviously there is more to look at when buying the skimmer but this is one of the main parameters.

My skimmer needs cleaning every second day because i feed heavily, and skimmer is very efficient in waste removal.
more pics and description on page one.

I clean mine when I change my filter sock about every 3 days.
I've got 80 gallons of water with 2 clownfish, a goby and a pygmy angel So maybe I'm a bit over cautious.
I do a 10 gallon water change every 2 weeks.

I love love love the skimmer I got from Wayne.
It's the easiest thing in the world to change and clean.
http://www.fishtanksdirect.com/Urchi...wMag5Pump.aspx

Overkill? just a teeeny bit.
that being said I'd rather clean my skimmer twice as often and forget about my filter sock! I HATE THOSE THINGS! EW!