I always gut my fish before freezing...only cuz I thought it was the thing to do. But others' experience with freezing in the round has given me pause to re-consider.
Same here, always cleaned but frozen with head on. Also partly because I figured returning the guts to the ecosystem would be better than composting (and less messy)
And I often freeze fish much longer than 30 days. If filleted and vacuum packed, it's good for many many months if not a year or more, but anything not sealed will freezer burn around the exposed edges.
I've had some pretty old fillets dug up from the bottom of the freezer that were badly burned around the edges, but after cutting that part away, the meat that was protected by the skin & scales seemed perfectly fine.
If kept un-gutted, I now wonder how long it might take before the quality starts to suffer in a deep-freeze? Years? Maybe if there's no exposed meat, an intact frozen fish might have a very long freezer-life...
Going to try some like that this year.