Obviously, I can't speak for Xtol, but in general, you should never freeze photographic chemicals. First of all, even refrigerating them can cause components to fall out of solution. These may or may not redisolve when warmed up. Also, since the makeup of the solution changes, the solution may actually age faster if the preservatives are knocked out of solution. Secondly, unless you have a freezer dedicated to photographic use, you run the risk of contamination. Remember that when liquid freezes, it expands, which can lead to ruptured or leaking bottles.(posted 8289 days ago)A better solution is to get multiple brown glass bottles, and filling each. The aging will be minimized until you open the bottle.
David Carper ILFORD Technical Service