If the starbases have phasers like the verteron array (which has sufficient range to precisely shoot Starfleet Command on Earth from Mars) then parking a fleet at primary worlds might not be needed. However, we know Earth either has a dedicated fleet or a fleet nearby on call. The Wolf 359 fleet is called together on fairly short notice and that comprised 30 ships. The fleet which met the Borg Sphere in "Endgame" (not the 7 which escort Voyager after the Sphere's destructino) is almost 30 ships with minutes, instead of hours, to assemble.
Even there the 359 fleet was very much a desperate mismatch of everything and anything available within range, large or small, highly armed or not, modern or (mostly) outdated, many of which would have simply been passing through on other more mundane assignments and hardly constituting a standing defence fleet.
As for the Endgame fleet, there we see a totally different scenario, with Earth having not long since been attacked by the Breen, a conventional military power as opposed to some uber tech powered alien threat. Yes the war is over but nonetheless the only treaty we saw signed was with the Dominion, not the Bree with whom relations may yet sour. It only makes sense that many of the wartime precautions would still be in place, which by definition implies a totally different strategic philosophy to peacetime deployments.
In fact, looking at the composition of the two fleets above is instructive by itself. The Endgame fleet contains a Prometheus, at least one Nebula, a Defiant (I think), and generally presents as a high end mobile response operating deep within Federation space under wartime conditions. The 359 fleet on the other hand is a low level affair by comparison, which Admiral Hansen openly states he cobbled together from whatever was available (Mirandas and similar or lower level workhorses being prevalent as far as we can tell), indicating that the peacetime Federation operates no dedicated home defence fleet as such.