I buy a lot of shrimp and scallops frozen. They come in resealable bags, and I eat a bit at a time, reseal, then eat more later. How long can I do this before the shellfish go bad? I cooked some shrimp today from a bag I'd previously opened and resealed, and while the use-by date hadn't yet passed, they smelled different than usual, so I tossed them. Any guidelines on safety around this? I got seafood poisoning from restaurant mussels soon after I started eating seafood so I'm very paranoid now about this issue. Thanks.