I just cleaned mine out from 4 years sitting in a box after being put up from a tank that crashed without power for a week... Put it in a box never even thought or felt like cleaning it, just blah about it all after that. Dumped it in a tub of vinegar:water (1:10) and let it soak for an hour. Rinsed with COLD water (you don't want to crack the acrylic) and hooked it up. Also if the plugs have any buildup put them in a glass with a tsp of baking soda and a dash of salt. add vinegar and let soak for 15-20 minutes. It'll all be like new, and in my case the skimmer works better than EVER. I did all of my equipment in this tub though, and when the powerheads started working again I let them run for a few minutes as well.
My corallife skimmer has NEVER worked BETTER in the entire time I used it! It pulls a full cup in a few days time now with a cycling tank, vs a fully stocked tank before it barely pulled 1/10th of a cup in a full week (usual maint. time for the tank was saturday). Apparently it just needed to sit for a few years. LOL. I honestly had planned to replace it for my tank and EQ to be fully functional, but now you couldn't pay me to swap to another one haha. (ask me that after it decides to flood my room again though, that was the problem I had in the past with it)
(the gray/black cap on the collection cup can take some effort sometimes, get it a little warm with a hair dryer and twist and pull at the same time, worked wonders for me)