According to one answer on the Nikon P520 user forums (http
/www.nikonusa.com/en/Nikon-Products/Product/Compact-Digital-Cameras/26397/COOLPIX-P520.html) the maximum length is 29 minutes. "The maximum movie recording time(maximum movie length for a single movie)is 4GB or 29 minutes, even when there is sufficient free space on the memory card." This is not uncommon with digital cameras (some Panasonics may be the exception) and DSLRs.