The Fixed-term Parliaments Act significantly reduces the powers of the Prime Minister to manage the risk of government termination and to time elections to his or her party's advantage. In this paper we ask how the Act is likely to change the way in which governments terminate, their durability and opportunities for planning in government and departments. In answering these questions we draw on quantitative comparative evidence from other European countries that operate with fixed-term parliaments. Our analysis suggests that fixing the parliamentary term can be expected to convert some opportunistically called elections into regular elections and to stabilise governments toward the end of the parliamentary term. But the Act is also likely to have unanticipated consequences in increasing governments’ vulnerability to failure before they reach the final sessions of Parliament. We explore these unanticipated consequences and outline their implications for governing style and Civil Service planning.