The Bush tax cuts actually expire due to a "hard" rule (after a quick Google check to make sure of terms, you can call it the Byrd Rule to Reconciliation); in order to pass budget/monetary changes without dealing with amendments and fillbusters, there's a rule that says you can get certain laws pushed through without having to file closure -- but those laws have to pass a close check against the rules allowing such, AND have to expire after 10 years max. So it's not the same case as with the Brady bill, but the Byrd rule might have inspired the timeframe of the Brady bill's time-limited sections.