I'm always using Old Modules. In fact, 90% of all the modules my group played in 4e and 5e were derived from classic 1e/2e/BECMI/Dungeon modules... including the complete Dragonlance series, the GDQ saga, Lost City, Saltmarsh, Fire Mountain, Gauntlet/Sentinel, Tharizdun, Tsojcanth, and too many...