Personally, I would not recommend freezing these tartlets due to the meringue topping. Meringue is liable to absorb moisture during the defrosting process and many people find that these lose their light airy texture, becoming a bit rubbery. If wanting to freeze, I would suggest freezing prior to making the meringue topping. Once the curd is set and the shells cool to room temperature, place these on a baking sheet or plate in the freezer to freeze for two hours until solid. Remove from the plate and add to a freezer safe container to return to the freezer. These will keep for up to 3 months. Defrost in the refrigerator overnight, then top with fresh meringue for serving.