I'll try and lay out (in reverse chronology), Australian history on this. I will put the times a PM has been removed from office by their party in bold.
Tony Abbott (Liberal) - PM since late 2013, has just survived a leadership challenge after less than a year and a half in office. It may not be last one.
Kevin Rudd (Labor) - PM (for the second time) from the middle of 2013. Removed from office by losing a general election.
Julia Gillard (Labor) - PM from 2010. Removed from office by her party in her (technical) second term after three years in office.
Kevin Rudd (Labor) - PM (for the first time) from 2007 until 2010. Removed from office by his party in his first term after nearly three years in office.
John Howard (Liberal) - PM from 1996 until 2007. Removed from office by a general election, after serving four terms.
Paul Keating (Labor) - PM from 1991 until 1996. Removed from office by a general election, after serving nearly two terms.
Bob Hawke (Labor) - PM from 1983 until 1991. Removed from office by his party in his fourth term after 8 years in office.
Malcolm Fraser (Liberal) - PM from 1975 until 1982. Removed from office by a general election during his fourth term after seven years in office.
Gough Whitlam (Labor) - PM from 1972 until 1975. Sacked by the Governor General during his second term, after three years in office.
Sir William McMahon (Liberal) - PM from 1971 until 1972. Removed from office by a general election after just over a year in office.
Sir John Gorton (Liberal) - PM from 1968 until 1971. Resigned from office/removed by party (the vote on his leadership was tied - and he cast the deciding vote to end his own Prime Ministership - so it's hard to classify this one) after three years and one term.
Sir John McEwan (Country Party) - PM for less than one month at the end of 1967/start of 1968 - only ever intended as a short term caretaker until the Liberal Party could select a new Leader.
Harold Holt (Liberal) - PM from 1966-1967. Died in office (technically speaking he vanished without trace while swimming, and was declared dead). PM for nearly two years.
Sir Robert Menzies (Liberal) PM (for the second time) from 1949 until 1966. Resigned from office during his seventh term, after just over fifteen years in office.
Ben Chifley (Labor). PM from 1945 until 1949. Removed from office by a general election after just over one term and four years.
Frank Forde (Labor). Prime Minister for one week in 1945. Only appointed as a caretaker until the Labor Party could elect a new leader, although he did run in that election and lost to Chifley.
John Curtin (Labor). Prime Minister from 1941 until 1945. Died in office after just over one term and four years as Prime Minister.
Arthur Fadden (Country Party). Prime Minister for just over a month in 1941. Resigned from office when he could not guarantee supply. Because of the war situation demanding stability in government, more or less voluntarily handed over control to John Curtin - in peacetime, he would have fought on, but he judged (rightly in my view) that Australia couldn't afford to be wasting time on a constitutionally avoidable election.
Sir Robert Menzies (United Australia Party). Prime Minister (for the first time) from 1939 until 1941. Resigned from office midway through his (technical) second term, to avoid the instability of a leadership challenge in time of war.
Sir Earle Page (Country Party). Prime Minister for three weeks in 1939. Only intended as a temporary caretaker until the United Australia Party could elect a new leader.
Joseph Lyons (United Australia Party). Prime Minister from 1932 until 1939. Died in office in his fourth term after seven years in office.
James Scullin (Labor). Prime Minister from 1929 until 1932. Removed from office by a general election, in his second term after three years in office.
Stanley Bruce, 1st Viscount Bruce of Melbourne (Nationalist). Prime Minister from 1923 until 1929. Removed from office by a general election after two terms and six years.
Billy Hughes (Labor/Nationalist). Prime Minister from 1915 until 1923. Resigned from office after eight years during his third term.
Andrew Fisher (Labor). Prime Minister (for the third time) for most of 1915 (and the end of 1914). Resigned from office after about one year.
Sir Joseph Cook (Commonwealth Liberal). Prime Minister from 1913 until 1914. Removed from office by a general election. Andrew Fisher (Labor). Prime Minister (for the second time) from 1910 until 1913. Removed from office by a general election after one term and three years.
Alfred Deakin (Commonwealth Liberal). Prime Minister (for the third time) from 1909 until 1910. Removed from office by a general election after one year in office.
Andrew Fisher (Labour). Prime Minister (for the first time) from late 1908 until 1909. Removed from office by the Governor General appointing a new government without a general election (two small parties merged to form the Commonwealth Liberal Party, which combined had more seats than Labour).
Alfred Deakin (Protectionist). Prime Minister (for the second time) from 1905 until 1908. Removed from office by Parliament losing confidence. (He had only held government with the support of the Labour Party, which withdrew their support).
Sir George Reid (Free Trade). Prime Minister from 1904 until 1905. Removed from office by Parliament losing confidence (he could only hold office while the Protectionists and Labour party were feuding).
Chris Watson (Labour). Prime Minister for about four months in 1904. Resigned from office, having only taken office because it was refused (initially) by George Reid.
Alfred Deakin (Protectionist). Prime Minister (for the first time) from late 1903 until mid 1904. Resigned from office after less than a year.
Sir Edmund Barton (Protectionist). First Prime Minister of Australia from 1901 until 1903. Resigned from office to become a High Court Judge (which was the job he really wanted - he was a Constitutionalist, who only took the role of Prime Minister at the request of the first Governor General to ensure that government was set up on the principles of the new Constitution - there was initially tension and it needed a firm guiding hand. Once he'd ensured that was in place, he moved on).
I know this is long, but I think it shows that it really is quite unusual in Australia's history for a Prime Minister to be changed by their party. It has happened a few times, especially recently, but historically it is unusual.
You say "long",I'd describe it as very thorough indeed.Someday I hope to know one-tenth as much about my country's history as you clearly know about yours!
As for changes of leadership in national Parliaments I would think that they'd be kept to a minimum...apart from as a result of elections...for fear of alienating voters and creating a sense of instability,which one might expect in some nations but not in Australia.Your post clearly suggests that Oz has avoided that "instability".