A/C vents

[Marty]

Having baseboard heat, when central a/c was installed, as there was no pre-existing duct work, the air-handler was placed into a hallway/attic wall and duct work was installed n attic and through a wall to reach the lowest level of home. At the end of the a/c season, I put a new filter into a garbage bag and put it into the return, replacing the dirty filter. I do this to prevent possible cold air from infiltrating from the cold attic duct work into the home. Is it necessary to close all the ceiling vents?