Complex sentence: Bearss started interpretative touring as part of his official duties in Vicksburg, doing eight one-hour tours a day, but even though he was no longer required to do so after 1958, he kept it up as an avocation on weekends.
Split into simpler sentences: Bearss started interpretative touring as part of his official duties in Vicksburg, leading eight one-hour tours a day. Although he was no longer required to do so after 1958, he kept it up as an avocation on weekends.