Nick Clegg has defended plans for five-year fixed-term parliaments, arguing they are essential to the coalition's efforts to restore faith in politics.
The deputy PM was questioned by the Lords' constitution committee, which asked why four-year terms were not on offer instead.
But Mr Clegg said five-year parliaments allowed time to "govern properly" before election campaigning began.
Peers suggested five years was "rather cosy", as it offered MPs more security.
Mr Clegg has faced criticism of his plans for political reforms - which include moves to allow voters to "recall" MPs guilty of serious wrongdoing, to introduce fixed-term parliaments and for a referendum on the "alternative vote" for Westminster elections.
'Messiness on edges'
But he told peers the measures represented "a significant step" towards making Parliament more accountable and more in step with the needs of British society.
He said: "Do they themselves individually or collectively represent a sort of perfectly formed constitutional moment? No, I accept that there is always messiness on the edges of these things."
But he said many of the proposals "go very much with the grain of debates that have been raging for a very long time" and said there was a lot of political support for fixed-term parliaments.
Committee member Lord Rodgers suggested that five-year parliaments were a "rather cosy arrangement", as MPs would have "a sense of security for five years" and there would be fewer elections than under the current system.
Mr Clegg said he did "not believe there was a scientific link between the frequency of elections and the quality of government".
He argued that about 10 elections since World War Two had resulted in a parliament lasting longer than four years, and three of the last five had seen a government in power for five years.
Mr Clegg said: "It's a combination of providing a length of time with which people are familiar and which allows governments at least maybe four of those five years ... to get on with governing properly for the benefit of the country, combined with taking away from the executive this ability to capriciously time the election for nothing more than political self-interest."
'Hamstrung and paralysed'
He said governments tended to be "hamstrung and paralysed" for at least a year before a general election, so a five-year term would allow four years to "get on and do difficult things".
There has been some complaint that the fixed-term parliaments bill has not been published in draft to undergo further scrutiny. Crossbencher Lord Pannick asked Mr Clegg: "What's the rush?"
Former Attorney General Lord Goldsmith suggested that, as the prime minister had said the next election would be held in 2015, that there should be "adequate time for the people, for Parliament, really to debate these fundamental changes".
But Mr Clegg said the government had consulted with "institutions which have a constitutional role" and had been warned that simply making a commitment to hold elections in 2015 then having a "more leisurely approach" could have left it in "limbo".
The bill would be subject to the "greatest possible scrutiny" as it made its way through Parliament, he said.
He also suggested that questions over the role of the Queen - who officially dissolves Parliament at the prime minister's request - had played a part in the decision.
"I think one is treading on relatively sensitive ground for that reason, amongst others, and... that it was better to try to get this right in a binding fashion."
The five-year pattern would mean that the UK-wide election of 7 May 2015 clashed with those in the devolved assemblies and would continue to do so again once every 20 years.
Mr Clegg argued that there would have been clashes anyway under the current system. He said there was some potential for confusion with two legislative elections on the same day and the government was consulting to see if there were "alternatives" but there were "no easy answers".