I've come across a roll of prepreg that's been sitting in the freezer for quite a while. It looks fine, but I'm not sure whether it's still usable.
The first thing to check is the manufacturer's shelf life and expiry date. If the material has been kept at the correct temperature the whole time and is still within its stated shelf life, it should perform as intended. Once the shelf life has passed, manufacturers generally cannot guarantee the processing behaviour or the final mechanical properties. For non-critical work some people choose to test older material first, but for structural components it is best to stay within the manufacturer's recommendations.
Ask the Allbase team and we'll add the answer here for everyone.