Depends on the oils. Citrus, especially orange, oils tend to go "off" pretty quickly. Some others actually improve with age (patchouli comes to mind).
If you store your EOs properly - in amber glass in a cool location with constant temperatures - then you can get several years out of most (assuming your supplier hasn't had it for several oils before you get it!).
Regarding crystals - vanilla and a few other things do crystallize out at cooler temps. No harm done, just warm the oil in a water bath and move forward. BUT many temp shifts are not good for your oils, so if you intend to keep a vanilla oil chilled you should portion it off so that you don't need to keep re-warming the same oil.
As a fragrance manufacturer, we keep our EOs at varying temps depending on the oil, but we rarely go down to 40F (refrigerator temp) for most.