Not in my experience, or anyone else's here that I am aware of. Freezing in my freezer does not separate the components, and VG certainly does not degrade in the freezer. In mine the liquid does not freeze entirely, rather just gets VERY thick. I suppose if one were to take it down to MUCH colder temperatures, where the solution freezes solid, there might be some separation. But I'm not even sure a SubZero freezer (~-10F) would freeze a liquid solid.
ZoiDman is correct, freezing DIY nic is like hitting the pause button. I have 5.5 year old nic in my freezer that is the same as when I first stored it. No changes at all that I can detect with my eyes.
Even at room temp, nic lasts quite a while without significantly losing potency...although trace nic-oxides that will form will add TH and "pepper effect" and maybe some light tobacco-like taste to it. Still fine to vape, even if very yellow. Glass will slow this down too. I typically have one or two 50 mL amber bottles of VG-nic out for usage for many weeks without significant change. If the nic is in typical dropper bottles, and not glass, it will oxidize faster when out at room temp, since O2 can get through the bottle wall.
Even if the nic does oxidize a bit, that is just fine with me, since I enjoy the added TH and flavor nuances that oxidizing create. In fact, controlled oxidation for this purpose is being done by VapersTek, called Throat Hit nic, and is my favorite of currently available nics.