There are manufacturers who claim their electrodes are 'vacuum' packed, but the packaging is totally bogus. If you get it in the foil packs, or a plastic box wrapped with tape... put it in a bake oven. Not a holding oven. Most of them aren't even close, the foil is ripped somewhere before you get it.
Use companies that supply them in sealed metal cans, either 10 or 50 lbs. The 10's have pop tops. They can also often be used up in a day so you don't have to worry about them. Most are, but make sure, as newinsp said, they are the 'R', 'M', etc ones. Those are good for 9 hrs and don't cost any more than the others. At least at my supplier.
Open the can, place most of it straight into a holding oven. That way there is no question how long it has been out. Use up the rest, grap fresh from oven.
I still have not had the problems mentioned by others in another thread with Excalibur. Mine continue to run great...3/32, 1/8, & 5/32. It is still my number one choice.
Have a Great Day, Brent