Might this have the unintended consequence of CVs only being used for port defense?
With only 60 minutes there may be some unintended consequences, this being probably one of them.
A time span like 180 minutes even gives ample time to get the port back. It would also be an incentive for the side that just captured the port still to go out and sink that CV, instead of just waiting for it just falling into your ands after only an hour.
After all, the main reason for this wish is not to provide an easy way to gain a new CV, but just to prevent them being out of the fight for a whole week.
All usually strategies for CV combat would still work the same, even bringing it out of the danger zone until the port is recaptured... only infinite hiding and not caring about it any more would be a thing of the past.