The big problem with stored records is mold growth on the vinyl and jacket which produces that mildew smell. This is worsened by humid environments. As long as you do not smell mildew and the records were not subject to heat you will be ok. If they were subject to heat the results will be rather obvious.
Records not stored vertically for decades
I’m looking to eventually get my vinyl rig back up n running and went to get my albums and found they’ve been lying flat probably for decades in two stacks of about 75 albums in each stack. Any chance they’re still in good shape, or what damage may have been done versus being stored vertically? They’ve been in a dry, temperature-controlled basement the whole time. No way to play them right now so just hoping they might still be ok. Thanks for thoughts.