I have stored batteries for 5 months many times.
Up here in NY, thousands of boats and RVs are stored, thru the winter, with batteries disconnected, year after year.
If you start with fully charged, good batteries and disconnect them, they will last 5 months and longer. I always separated all of them, in case 1 went bad, it wouldn't drag down the others.
Weak and failing batteries don't last and probably should have been replaced anyway.
If you only replaced one last spring, after having them all dead, expect to replace more this year.
Storing a discharged battery for less than a month, is a death sentence.