Yes you can freeze  unbaked tartlet shells for multiple weeks in an airtight bag or container I don’t recommend freezing baked tartlet shells, as they would become soggy. Keep those at room temperature in an airtight container for up to a week. If you can, place a desiccant in the container. And if the shells are a bit soft when you want to use them, recrisp them in the over for a couple of minutes before using them.