Mason jars seal much better than tins. This time of year, if I'm not going to finish it within a week, I will always jar it up. When it is more humid, it will last in the tin a couple weeks. Also, not all tins are created equal. The rectangular ones don't seem to seal very well. The circular pop tins sometimes seal ok. The best tins for resealing are the circular screw on type, or the Reiner paint cans also seem to seal well.