Hopkins continued his career as a session and touring musician with a variety of acts, including Jefferson Airplane, the Rolling Stones (most notably on "Exile on Main St." and the group's ensuing 1972 American tour), the Jerry Garcia Band and Joe Cocker. He died in September 1994 from complications resulting from intestinal surgery related to his lifelong battle with Crohn's disease. In the 1980s, he joined the controversial Church of Scientology and credited the organization's Purification Rundown with vanquishing his long struggle with substance abuse. Valenti underwent brain surgery for an arteriovenous malformation in the late 1980s; despite suffering from short-term memory loss and struggling with the adverse effects of anti-convulsive medications, he continued to write songs and perform with various Marin County musicians until his sudden death in November 1994.