Made the exact same mistake with my old Simpsons tapes from the 90s. Had them stacked sideways in a cardboard box in my garage for like 8 years because I figured as long as they were out of sunlight they'd be fine. Nope. Pulled them out last summer and half of them had that wavy picture and the tracking was all over the place. Turns out heat and humidity in the garage did way more damage than I ever thought. Now they live in plastic bins in my closet with those little silica packs. Lesson learned the hard way.