Remote Starfleet stations could act as hubs for reserve ships kept in the vacuum of space. Even if hull preservation is comparatively easy, the ships still require caretakers and a personnel plan for reactivation. The source material offers no clear formal reserve service, suggesting that the Federation relies on its enormous population, long-lived species, and depth of former personnel. Possessing stored equipment is a different capability from maintaining the organization needed to make it operational.
Notable Point · 53:37-56:33
A reserve fleet needs crews as well as stored hulls
Space makes long-term hull storage plausible, but dormant ships have little wartime value without caretaker forces, trained crews, and a system for mobilizing personnel.