Break in period

What would the forum say about how long or how many hours of play time needs to occur before you can establish that your new loudspeakers are playing at optimum performance? I've heard opinions on this all over the scale!! Does this depend on the type and brand of loudspeaker, material of drivers, power being driven, etc? Can we agree on a nominal time period? I realize it may also depend on how loud you play them as well. Any thoughts? Many thanks.