staling

Hello All, I make a 9" sandwich loaf (sub style) that is some-what like a French bread.I am pleased with the crust and crumb, but unfortunately it stales and become quite hard after about 10-12 hours. If I put the loaves in a plastic bag then the crust becomes way, way too chewy. I have been freezing some of them and that seems to work semi-ok. Is there any way I can make a loaf that will last 36-48 hrs. Any ideas would be much appreciated. P.S. I use a 18 hr sponge and the only other ingredients are bread flour, water, yeast and salt