I scoop out the marrow, and then freeze them in individual ziploc bags. I give them to Molly frozen. Just bought 3 for her yesterday

I don't refreeze them since I scoop the marrow out anyway. When they are empty she gets peanut butter in them or I will melt cheese in one and let it cool. She usually chews on an empty bone when she is tired, so I keep some in her toy basket for her. I throw them away if I see a crack in it.