I've had records that were stored flat for months to years and never had an issues with them. I think as long as they weren't submitted to excessive heat or humidity they'll be fine.
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.