As Jonathon mentioned, phenol should not be oxidized (once it is oxidized it turns to pink color) take care about that. Generally equilibrated phenol can store either at room temp or 4 C. You can store as long as you want provided it should not be oxidized.
The main problem is that phenol oxidises with age, and this can affect the quality and yield of you DNA. If you are going to make it fresh you will have to redistill it before adding the chloroform/isoamyl alchohol, but it is best to buy very pure solutions that are redistilled already- phenol is nasty and any reduction in manipulation is a good thing. Some people add 8-Hydroxyquinalone to the mix when it is being made, which acts as an anti-oxidant preventing phenol oxidation- this turns the solution yellow. I would not use the solution beyond 6 months as phenol goes pink then yellow when oxidised, and so you would not be able to tell if has oxidised or not with 8-Hydroxyquinalone in it. Store it carefully in brown glass wrapped in tinfoil at 4C. Jonathon makes a good point about buying it in the most appropriate quantities, if you only want to do a few mini-preps, don't buy 5 litres! it is a real hassle to dispose of correctly and safely!