Well, stacking enough food for everyone in a ship (which likely possess thousand of crew, plus transporting ground troups) for a year campaign is a bit hard : it will take too much place on a ship , can you imagine a several month-stock of food and water for tens of thousand of people and soldiers ? Plus you have the attrition in term of ammo, fuel, etc . Even in maintenance and reparation. I personnaly doubt people will stack all of that in each ship, I think they would prefer supply lines.
From what I remember, in the Foundation serie of Asimov, Bel Riose is establishing supply lines. They don't stack up tons of food in each vessels. And generally speaking, I think that in most sci fi universes, fleets are split up both for defensive purposes and for supply problems. Smaller fleet are easier to supply and can just pillage cargos and planets.
Honestly, it isn't totally unbelievable to have some kind of "attrition" (decrease in combat effectiveness ? Massive increase in cost ? I dunno ) , which will be realistic while partly resolving the problem.