Here are a couple rules of thumb for dealing with used fryer oil. This comes from some cooking classes taken in years past.
Generally speaking, any fryer oil that was used to fry a protein in the household environment should be discarded. Reason being is that you are just not going to use the oil frequently enough for it to last and most households don't have the filtration equipment necessary to get contaminants out of the oil. Restaurants typically change out their oil at least once a week and filter once a day.
If you are frying non-proteins at home, you can save and re-use it 3-4 times if you filter it through a couple coffee filters first. Used oil can be stored in the same container it came in and in a cool, dry, dark place for up to a couple months (two, perhaps three).
You should *NOT* put used oil in the fridge or freezer. Moisture will develop with the change in temperature and this will become enormously dangerous when the oil is re-introduced to the fryer.
Those of us who fry with any regularity know that optimum flavor isn't achieved until the 3rd or 4th fry cycle. If you fry foods often enough, take some of your used oil and put it in with your new oil before frying. This way, you are starting out with some of that "goodness" in your new batch of fry oil.