If you use the Chicago Mercantile Exchange for any risk management of your Class III Milk, you can start trading 24 hours a day!
This week, the CME began trading contract on the Globex platform, and will trade simultaneously with the open outcry market during the day. The idea of the electronic contracts is typically to add more investors, although past history has shown that the electronic contracts trade mere fractions of the volume their open-outcry brethren exchange.
Ultimately, the decision to use these contracts is really up to you and your risk management professional. The variance between the price and bid between the electronic and outcry contracts will vary, but should be negligible for most producers.