I do mine up in the summer for the winter so.... about 6-9 months is about when I get them used up. You could probably keep them longer because they get like giant solid ice cubes. I usually try to use all my freezer supplies in the 6-9 month time frame. I know that the frozen food guide says to use up frozen stuff within a year to avoid freezer burn. I don't know that the tomatoes would get freezer burn because you are removing the skins when you take them out.