Under admin CP > spam management
It appears do for one, it does for all. Currently 30 seconds.
Minimum Time Between Posts
You may prevent your users from flooding your forum with posts by activating this feature.
By enabling floodcheck, you disallow users from making another post within a given time span of their last posting. In other words, if you set a floodcheck time span of 30 seconds, a user may not post again within 30 seconds of making his last post.
Administrators and moderators are exempt from floodcheck.
Recommended: 30 seconds. Type the number of seconds only. Enter 0 to disable this function.