One of the odd quirks about politics in 2015 is that neither the Prime Minister nor the Leader of the Opposition expected to win. The Conservatives’ manifesto was written with the expectation that the Liberal Democrats would water it down – when Jeremy Corbyn entered the Labour leadership, the best-case scenario for many of his backers was a strong enough showing to guarantee the left a seat at the top table under whichever candidate of the right emerged as leader.

That’s part of why many of Corbyn’s closest allies – let alone his many opponents on either side of the House of the Commons – expect him to stand down before the general election. One supporter of Corbyn told me there was “no chance” of the Islington North MP making it until 2020.

But it is astonishingly difficult to remove a Labour leader if they don’t want to go – as opponents of both Gordon Brown and Ed Miliband discovered. While the Conservative Party might have been able to remove Iain Duncan Smith just days after he was applauded by Tory party activists, Labour is a different beast. Unless the membership decides that Corbynism is the road to ruin, which seems highly unlikely, Corbyn will remain in place until he decides to retire – or he is defeated at a general election.

That’s increasingly the view of Corbyn’s internal opponents. One MP remarked to me that “only the members can get rid of Corbyn”. But many of his allies believe that he could step down in 2017, or 2018, to pave the way for a chosen successor, perhaps Clive Lewis, a former soldier and BBC journalist, with impeccable Corbynite credentials. “You can’t say that Clive is a threat to national security, can you?”

Their case is simple: at the time of the 2020 election, Corbyn will be 70. He was widely expected to stand down at the next election, particularly if Cat Smith, his former staffer, longtime ally and now MP for the marginal seat of Lancaster and Fleetwood, had failed to win. Why not stand down to allow the likes of Lewis, or Richard Burgon, or his PPS, Kate Osamor, to succeed him?

It’s a persuasive case – and, for centrist MPs who believe that Corbyn’s victory owed as much to Corbyn’s own qualities as his policy platform, provides the hope that a different candidate: Tom Watson, or Dan Jarvis, might manage to frustrate the succession.

Are they right? Well, five years is a long time. Local elections – and a hostile press – might mean Corbyn decides to call it quits. But the early signs all point to Corbyn being in it for the long haul.

His conference speech hinted at it. Aides briefed that it would last 45 minutes – it was close to an hour, partly due to references to Maya Angelou, Ben Okri and the Saudi dissident Ali Mohammed al-Nimr, that were slipped by the Labour leader personally. “Jeremy’s enjoying this,” commented one supporter.

Corbyn’s early appointments – both to his Shadow Cabinet, where he ensconced a genuine ally, John McDonnell, rather than using it to balance the party, as many suggested – and to his office, suggest he is in for the long haul.

Seumas Milne, on a loan deal from the Guardian, as director of communications the former Ayr MP Katy Clark and Andrew Fisher, his policy adviser, aren’t the appointments of a man looking to keep the parliamentary Labour party on side for two years while he changes the rules of the party to “futureproof” Labour against a counter-revolution from his internal opponents. These are the picks of a Labour leader who is filling his office with close and trusted allies, who he believes are capable of getting him to 2020 in the best shape to win the election.