The documentation on Accounts and Audience Explorer notes that “the Lifetime date option displays activities up to the last 90 days. To filter older activities, use the Custom Date Range option to specify a time period of up to six months at a time.“
Given the adjacent options of ‘Last [7, 14, 28, 30] Days’ it is at least counterintuitive that Lifetime would = Last 90 Days. This should just be labeled “Last 90 Days”