Complex sentence: Alix served as regent when her husband left for the East, and since their son was underage, she continued as regent for several years after Theobald's death in 1191.
Split into simpler sentences: Alix served as regent of Blois on several occasions, such as when her husband left for the East and their son was still underage. She also continued to serve as regent for several years after Theobald's death in 1191.