Depends on the kit. My Wilson Benesch speakers took several weeks before they really started to give their best. The speakers I used with my Onkyo CR515DAB took a couple of hours, if that.
Testing the frequency responses of speakers (primarily woofers) has found they can change over a period of a few hours and if kept in regular use, retain that frequency response. But if allowed to rest over a period of days or even weeks they will return to their original state. Amps warm up rather than break in.