Hi all, I'd like to make these for a party on May 4th. I'm thinking of a sesame vinaigrette, with shallots, garlic, and chiles. Having never made these before, I don't know how far ahead to start them, and what happens if they sit too long. Also, with garlic in the mix, when do they become unsafe to eat? Does the vinegar do anything to preserve it? Please add any comments, tried and true methods,or ideas. Thanks!