From the blog "Conglomerate"

Conglomerate - Limits of Skyrim     250 (of 256) active plugin limit for Skyrim LE Active esp and esm Plugins count against that limit Max Plugins: 250 from my experience lower is better. A lower number also allows to add plugins later to the game at the end of the LO Symptoms with  >250 Plugins: game becomes unstable CTD randomly on game start (restarting directly after th